"iu 


-^^K 
^^\^. 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


y 


y. 


^ 


1.0 


I.I 


l;;|28     |2.5 

i^i  1^    |||2.2 


m 


It  lifi  IIIIIM 


1.8 


-    6" 


11.25  III  1.4    ill  1.6 


V] 


Si 


<?^' 


^ 


VM 


7 


7 


Photographic 

Sciences 

Corporation 


23  WEST  M.  i!    STREET 

WEBSTER,  N.Y.  14S80 

(716)  872-4503 


CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  Canadian  de  microreproductions  historiques 


Technical  and  Bibliographic  Notes/Notes  techniques  et  bibliographiques 

The  Institute  has  bttenioted  to  obtain  the  best 
original  copy  available  for  filming.  Features  of  this 
copy  which  may  be  bibliographically  unique, 
which  may  alter  any  of  the  images  in  the 
reproduction,  or  which  may  significantly  change 
the  usual  method  of  filming,  are  checked  below. 

L'Institut  a  microfilm^  le  meilleur  exemplaire 
qu'il  lui  a  6t6  possible  de  se  procurer.  Les  details 
de  cet  exemplaire  qui  sont  peut-Atre  uniques  du 
point  de  vue  bibliographique,  qui  peuvent  modifier 
une  image  reproduite.  ou  qui  peuvent  exiger  une 
modification  dans  la  m^thode  normale  de  filmage 
sont  inJiqu6s  ci-dessous. 

Coloured  covers/ 
Couverture  de  couleur 

— 

Coloured  pages/ 
Pages  de  couleur 

Covers  damaged/ 
Couverture  endommagie 

— 

Pages  damaged/ 
Pages  endommagdes 

Covers  restored  and/or  laminated/ 
Couverture  restaur6e  et/ou  pelliculie 

— 

Pages  restored  and/or  laminated/ 
Pages  restauries  et/ou  pellicul6es 

Cover  title  missing/ 

Le  titre  de  couverture  manque 

L/J 

Pages  discoloured,  stained  or  foxed/ 
Pages  d6color6es,  tachetdes  ou  piqu6es 

Coloured  maps/ 

Cartes  gdographiques  en  couleur 

Pages  detached/ 
Pages  ddtachies 

Th( 


Th( 
poj 
of 
filn 


Ori 
be( 
the 
sio 
oth 
firs 
sioi 
or  i 


□    Coloured  ink  (i.e.  other  than  blue  or  black)/ 
Encre  de  couleur  (i.e.  autre  que  bleue  ou  noire) 

I      I    Coloured  plates  and/or  illustrations/ 


n 


n 


D 


Planches  et/ou  illustrations  an  couleur 


Bound  with  other  material/ 
Reli6  avec  d'autres  documents 


Tight  binding  may  cause  shadows  or  distortion 
along  interior  margin/ 

La  reliure  serrie  peut  causer  de  I'ombre  ou  de  la 
distortion  le  long  de  la  marge  intirieure 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
II  se  peut  que  certaines  pages  blanches  ajout6es 
iors  d'une  restauration  apparaissent  dans  le  texte, 
mais,  lorsque  cela  dtait  possible,  ces  pages  n'ont 
pas  it6  filmies. 

Additional  comments:/ 
Commentaires  supplimentaires: 


D 
D 
D 
D 
D 


Showthrough/ 
Transparence 

Quality  of  pri.nt  varies/ 
Qualitd  indgale  de  I'impression 

Includes  supplementary  material/ 
Comprend  du  materiel  suppi^mentaire 

Only  edition  available/ 
Seule  (Edition  disponible 

Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc.,  have  been  refilmed  to 
ensure  the  best  possible  image/ 
Les  pages  totalement  ou  partiellement 
obscurcies  par  un  feuillet  d'errata,  une  pelure, 
etc.,  ont  6t<i  film6es  d  nouveau  de  fapon  d 
obtenir  la  meiHeure  image  possible. 


Th€ 
sha 
TIN 
whi 

Ma 
diff 
enti 
beg 
righ 
reqi 
mel 


This  item  is  filmed  at  the  reduction  'itio  checked  below/ 

Ce  document  est  filmA  au  taux  de  reduction  indiquA  ci-dessous. 

10X  14X  18X  22X 


26X 


30X 


7 


12X 


16X 


20X 


24X 


28X 


r»2X 


The  copy  filmed  here  h9s  been  reproduced  thanks 
n  the  generosity  of: 

University  of  Victoria 
IMcPhcrson  Library 

The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legib'iity 
of  the  original  copy  and  in  keeping  with  the 
filming  contract  specifications. 


Original  copies  in  printed  paper  covers  are  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  illustrated  impres- 
sion, or  the  back  cover  when  appropriate.  All 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  impres- 
sion, and  ending  on  the  last  page  with  a  printed 
or  illustrated  impression. 


The  last  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  —^(meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END  "). 
whichever  applies. 


L'exemplaire  filmd  fut  reproduit  grAce  d  la 
g6n6rosit6  de: 

University  of  Victoria 
McPherson  Library 

Les  images  suivantes  ont  6t6  reproduites  avec  le 
plus  grand  soin,  compte  tenu  de  la  condition  et 
de  la  nettetd  de  l'exemplaire  film6.  et  en 
conformity  avec  les  conditions  du  contrat  de 
filmaqe. 

Les  exemplaires  originaux  dont  la  couverture  en 
i^apier  est  imprimie  sont  filmds  en  commen^ant 
par  le  premier  plat  et  en  terminant  soit  par  la 
dernidre  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration.  soit  par  le  second 
plat,  selon  le  cas.  Tous  les  autres  exemplaires 
originaux  sont  film6s  en  commen^ant  par  la 
premidre  pagf  qui  comporte  une  empreinte 
d"impression  ou  d"illustration  et  en  terminant  par 
la  dernidre  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboles  suivants  apparaitra  sur  la 
dernidre  image  de  cheque  microfiche,  selon  le 
cas:  le  symbole  --*»  signifie  ""A  SUIVRE'".  le 
symbole  V  signifie  "FIN"'. 


Maps,  plates,  charts,  etc.,  may  be  filmed  at 
different  reduction  ratios.  Those  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  luft  hand  corner,  left  to 
right  and  top  to  bottom,  as  many  frames  as 
required.  The  following  diagrams  illustratr  the 
method: 


Les  cartes,  planches,  tableaux,  etc.,  peuvent  6tre 
film6s  d  des  taux  de  reduction  diff6rents. 
Lorsque  le  document  est  trop  grand  pour  dtre 
reproduit  en  un  seul  cliche,  il  est  fiim6  d  partir 
de  Tangle  sup6rieur  gauche,  de  gauche  &  droite, 
et  de  haut  en  bas,  en  prenant  le  nombre 
d"images  n6cessaire.  Les  diagrammes  suivants 
illustrent  la  m6thode. 


1 

2 

3 

1 

2 

3 

4 

5 

6 

^■/9^. 


THFi 


SPEAKING  TELEPHONE, 


TALKING  PHONOGRAPH 


AND    OTIIRU    NOVELTIES. 


gf:orge  b.  prescott. 

H.  M.  Pomproy,  M,  0. 
Los  Angeles,  Cal._ 


FULLY    ILLUSTRATED. 


NEW  YOI^K  • 

U.     Al'PLETON     &     COMPANY. 
1878. 


UNIVWSITY  OF  ViaOfU 

L.rfRARY 

Victoria,    8    C. 


KnteriMl,  jucoriliiiL'  tii  Acf  of  Cim>. 


:ri'<s.  in  till'  J  car  Is;n,  by 


GEORGE    B.   PRESCOTT. 


Ill  the  Ollice  i)f  tliu  Libniriuu  of  C'uiit 


:l"l'srt,  ut  \Vttsilill;'ton. 


PREFACE. 


The  object  wliicli  wo  liiivc  ],;i(l  in  view,  in  preparing  this 
work,  has  been  to  fnniisli  thi'  ublic  with  a  clear  and  accurate 
description  of  the  more  rccetii  and  useful  improveinouts  in 
electrical  science,  and  especially  to  explain  the  principles  and 
()]K'ration  of  tlint  marvellous  production,  the  Speaking  Tele- 
phone. In  giving  particular  prominence  to  tliis  part  of  the 
subject,  however,  we  have  by  no  means  lost  siglit  of  another 
matter  in  connection  therewitli.  of  considerable  historical  im- 
])ortance,  and  which  has  also  elicited  an  unusual  amount  of 
general  interest.  The  (juestion  as  to  whom  we  are  indebted  for 
the  telej)hone  is  one  which,  in  consequence  of  the  conflicting 
statements  that  have  ai)peared  from  time  to  time,  is,  to  s:iv  the 
least,  extremely  ])n/,;«ling.  We  have,  therefore,  endeavored  to 
give  it  the  attention  its  importanr  ,  demands,  in  order  to  arrive 
at  a  tru(!  solution  of  the  ]»rolilei;i,  and,  in  doing  so,  have  taken 
every  opportunity  to  consult  all  available  authorities  on  the 
subjet^t.  No  effort  has  been  spared  in  our  investigation  to 
obtain  all  the  facts  as  they  uro;  and  these  are  now  given  as 
we  have  found  them,  without  favor  or  jirejudice.  The  reader 
will  thus  1k!  enabhid  to  judge  for  him.self  just  what  measure  of 
credit  to  accord  to  eiich  of  the  dilTerent  experimenters  who 
have  been  engagcjd  with  the  ])roblem  of  electrical  transmission 
of  articulate  speech,  and  who.se  labors  have  been  crowned  with 
such  abundant  success. 


11 


PBEFACE. 


In  preparing  the  Inlroa.u;ti<.n,  vw  Ikut  been  m.icli  indobtod 
to  a  vtduabU"  and  int'^restin-  vv,n^n6  oi  tho  history  of  ck^ctri- 
ral  discovery,  by  Edward  N.  Dick.n-son,  Es,].,  in  an  eloqucM.t 
and  exhaustive  argument  made  by  hi.u  in  a  re(.ent  in.portant 
telegraph  cause  in  this  city. 


CONTENTS. 

•  >  ■ 

OlIAlTKlt.  PaOK. 

1. — Tlio  Si)eiikiiij5  Ti'lcpIioMO fi 

II. — Bell's  'rclupliDiiic    Hcsciirclios 00 

1 II. — The  TcIcplioiK'  Abroiul   8;i 

]V. — History  of  tlic  Produotiou  of  Galvanic  Music 110 

V. — Oniy'.s  Telephonic  Koscarchcs ISl 

VI. — •Kdison'.y  Telephonic  Re-Jearclics '218 

VII. — Kloctro-llarnionic  Telojii-apliy '235 

VI  n. — Dolbear's  Telephonic  Reseaiclics '2G0 

L\. — Iniprovcmcnts  of  Channinj;.  Bluku  and  oilu-rs 2'i 

.\,— The  Talking  Phouograph 292 

X  I. — Quadrnplox  Telegraphy •*"'' 

XII.  — Kloctric,  Call  Bolls :"5 

XIII.— The  Kloctric  Light  ^'lO 


Up( 

tliii 

V(-!' 

tha 

U)v 

\ 

out 

Slip 

gr;ij 

by 

froii 

trll 

botv 

decc 

tho 

obsc 

tho 


Ii 

defle 


INTR()r)ITCTIO:N" 

A 


WllKX  H'niiiklin  dnw  I'imip.  the  clouds  iIh;  chjctric!  spark 
iipoii  tilt!  cord  of  liis  kite,  it  scciiicd  oiivioiis  that  electricity 
Miiglit  be  luadc  use  of  I'or  the  piirposi;  of  telegnipliy;  and  more 
than  one  hundred  years  ago  Lesagc;  estul)lisliod  a  teh^graph  in 
(lencva  by  tlu-  use  of  frietionai  clecrtrieity.  Hut  tliis  force  had 
very  litll(  power  when  transmitted  over  a  long  distance,  and 
that  little  was  |n'aetieally  uneontnjlhihle,  and  therefore  useless 
ior  telegraphy. 

When  galvanism  was  discovered,  at  the  bcgiimingof  the  pres- 
ent century,  and  tlu;  voltjiie  battery  invented,  it  was  at  once 
su[)p()scd  that  this  new  form  of  electricity  might  work  a  tele- 
graph, and  ten  years  later  the  chemical  telegraph  was  invented 
l^y  Coxe,  in  Philadel])hia.  Under  this  system,  the  two  wires 
from  a  galvanic  battery  were  made  to  approach  each  other  in  a 
ci'll  of  water.  When  the  galvanic  circuit  was  closed,  the  water 
iK-lwecn  the  ojiiKjsite  poles,  which  were  near  each  other,  was 
decomposed,  and  a  bubble  of  hydrogen  rose  to  the  surface,  as 
the  bubble  from  champagne  does  in  the  wine  cup;  and  the 
observer,  seeing  it,  knew  that  a  current  was  passing,  and  that 
the  bubble  was  the  signal.     But  it  was  evanescent 

" like  snow  fall.s  in  tlio  livor, 

A  iiLinicnt  wliite,  tlicn  meltH  forovor.'.' 

In  1820,  Oei-stcd  discovered  that  an  electric  current  would 
deflect  a  magnetic  needle,  and  Arago  aad  Davy  simultaneously 


u 


INTUODUCTION. 


(liscovon'il  that  u  piece  of  irmi,  suiToiimled  ]>y  a  spiral  wirn 
tlimilgli   wliieli    ii.  eiiiTeiil  of   ;jiilviiiiism   piisscd,    would   heeonie 

iiuigiietic.      From  this  fact  Ampere  dedu 1  the  liypotiiesis  that 

in.'igiictism  in  tlie  circidatinu  of  ciirreiits  of  electricity  nt  right 
angles  ti)  the  axis  joining  the  two  poles  of  the  iiiagnot.  That 
was  a  hrilliaiit  deduction:  Imt  no  [)raetieai  resn.t  was  produced 
from  it  until  lS2r),  when  iIk^  first  sim[il(!  el(>(<tro-magtiet  was 
mado  by  Sturgeon,  who  i)cnt  a  pl( .  .  of  wii'O  into  the  sha[)e  of  a 
horsoslioe,  and  wound  a  lino  wireurourd  it  in  a  liciix,  through 
which  the  galvanic;  current  passcil ;  and  Ik;  found  that  the  horse- 
shoe wire  was  magnetic  as  long  as  tho  current  lloweil.  'I'hen 
at  once  an  attempt  wa.^  mad(!  with  Sturgeon's  magnet  to  produce 
the  clectro-magni'tie  telegraph,  but  without  success,  'i'lie  dilli- 
culty  was  that  the  magni'tic  power  <!ould  not  l)c  transmitted  from 
the  battery  for  more  than  lifty  feet  with  Sturgeon's  magnet, 
which  was,  therefoic,  entirely  \iseless  for  the  })ur|ioses  of  a 
telegraph ;  and,  in  IS2!),  Professor  Barlow  [)u!)lisheil  a  seientifie 
demonstration  m  England,  which  was  ai^ceptcd  by  tho  scii-ntilie 
world,  that  an  electro-magnetic  tclcgr;<ph  was  impossible  ;  which 
was  true  in  the  then  state  of  knowledge. 

In  1830,  Profes.sor  Henry  deduced  from  the  hyjjothesis  of 
Ainpiire  the  invention  now  known  ;i^  the  compound  electro- 
magnet. He  also  answered  the  demonstration  of  Barlow,  and 
proved  tliat  the  electromagnetic  telegraph  was  possible,  hi  the 
same  year  h(!  set  up  an  electro-magnetic  telegraph  in  Albany, 
over  a  lino  of  a  mile  and  a  half  in  length,  using  a  polarized  relay, 
the  armature  of  which  was  pivoted  so  as  to  vibrate  between  its 
poles  as  the  current  of  electricity  was  rcvei-sed,  thus  transmitting 
intelligence  by  sound. 

In  1831,  Professor  Faraday  made  known  his  discovery  of 
the  phenomenon  of  magnetic  induction. 


INTUOnrCTIoN. 


Ill 


In  IH'M,  (laiiss  iind  Wclicr  cdiistnictcd  a  lino  of  telcgnij)!!, 
contaiii'inj^  iibout  15,000  feet,  of  wire,  which  was  oporatcd  l)y  tho 
inagiu't()-elf.'etri(!  currents  jr<'iKM'at(;(l  in  a  coil  f  wire  when  the 
hitter  was  movcil  u|i  or  down  ii|>on  a  ])i'rnian(Mit  magnet,  around 
wliich  it  was  placed.  Tho  slow  oscillations  of  a  magnetic  needle, 
caused  hv  th(!  passage  of  the  ciu'rent,  and  whicli  were  ol)scrved 
throngli  a  glass,  furnished  the  signals  for  eorrcspoiidenee.  Sir 
William  Thomson  has  since  greatly  improveil  tho  latter  appa- 
ratus, and  thereby  given  us  the  licautifuUy  sensitive  mirror  gal- 
vanometer which  bears  his  minic. 

In  1837,  Stcinheil  di.M-overcil  the  important  fact  that  the  eartli 
would  serve  as  a  conductor,  thereby  saving  oiu-  wire  in  forming 
a  circuit:  Cook*^  invented  his  electro-magnetic  semaphore, 
known  as  the  needle  telegraph,  in  which  nee<lK's  swing  upon  the 
face  of  a  dial,  just  as  the  vanes  of  the  old  .semaphores  swung 
on  the  liill  tops:  Morse  invented  his  electro-magmtie  telegra])h. 
whicli  he  put  in  operation  between  lialtimore  an  I  Washington 
ill  1844:  and  Pago  discovered  that  a  musical  sound  accom- 
panies tho  di.sturbanec  of  the  magnetic  forces  of  a  steel  bar, 
when  pois(;d  or  suspended  .so  as  to  exhibit  acoustic  vibrations. 

In  1801,  Reiss  discovered  that  a  vibrating  diaphragm  could  bo 
actuated  by  the  human  voice  .so  as  to  cause  the  pitch  and  rhythm 
of  vocal  sounds  to  be  transmitted  to  a  distance,  and  reproduced 
by  electro-magnetism. 

In  1872.  Stearns  pcM'fected  a  duplex  .system,  whereby  two  com- 
munications could  bo  simultaneously  tran.smitted  ovei  one 
wire;  and,  in  1874,  Edi.sou  invented  a  (juadruplex  .system  for 
the  simultaneous  transmission  of  four  communications  over  the 
same  conductor. 

In  1874,  Gray  invented  a  method  of  electrical  transmission  bv 
means  of  which  the  intensity  of  tlie  tones,  as  well  as  their  jiitch 


IV 


INTUODI'CTION. 


and  rlnlluii,  t;uiilil  bo  reproiliiceil  at  ii  di.^tauL'c  ;  and  subseiniently 
conceived  tlie  idea  of  eoutrolliiig  tlie  formation  of  electric  waves 
by  means  of  the  vibrations  of  a  diapliragm  capable  of  responding 
to  all  the  tones  of  the  linnian  voice,  thus  solving  the  problem  of 
the  transmission  and  rej)roductioii  of  articulate  speech  over  an 
electric  conductor. 

In  1876,  Bell  invented  an  improvement  in  the  apparatus  for 
the  transmission  and  reproduction  of  articulate  s})eech,  in  whieh 
magneto-electric  currents  were  supcri)osed  nj)on  a  voltaic  cir- 
cuit, and  actuated  an  iron  diaphragm  attached  to  a  soft  iron 
magnet. 

During  the  same  year,  Dolbear  conceived  the  idea  of  substitut- 
ing jiermanent  magnets  in  place  of  the  electro-magnets  and 
battery  previously  employed,  and  of  rising  the  same  instrument 
for  both  .sending  and  receiving,  in.stead  of  eniploying  instru- 
ments of  difTerent  construction,  as  had  been  previously  done. 

In  1877,  Edison  applied  to  the  telephone  the  discovery  made 
by  himself  a  few  years  before,  of  the  variation  of  resistance 
whieh  carbon  and  certain  otlier  semiconductors  undergo  when 
subjected  to  a  change  of  pressure.  By  this  means  he  n<jt  only 
succeeded  in  varying  the  strength  of  the  battery  current  in 
unison  with  the  rise  and  fall  of  the  vocal  utterances,  but,  at  the 
same  time,  also  obtained  louder  articulation 

Thus,  the  last  link  in  the  long  chain  has  been  completed,  in 
the  production  of  tiiat  marvellous  invention,  the  .speaking  tele- 
phone. In  that  machine  the  sj)caker  six'aks  to  a,  plate  of  soli<l 
iron,  and  the  voiee  of  the  sj)eaker  is  (ronverted  into  electricity. 
That  voice,  ojierating  njion  the  eleetro-ma^.ict  of  Prof.  Ilenry, 
generates  a  current  of  electricity,  which,  ilowing  over  the  line  to 
thedi.stant  station,  excites  magnetism  in  a  corresponding  magnet, 
and  sets  in  vibration  ii  plate  of  iron  similar  to  that  to  whieh  the 


INTKomCTlON. 


PiieiikiT  s]ic;iks  :  iiml  tliat  plate  speaks  h)  tlie  listener.  It  speaks 
with  tii<'  tones  of  tlio  luinum  voice;  it  speaks  so  that  if  tlirco 
people  are  talking  at  on.e  end,  each  of  their  voie(>s  is  distin- 
guished at  the  other,  and  yon  hear  them  all  as  if  you  stood  in 
their  prcsenee.  That  is  th(>  erowniiiLC  aehicvement  of  the  eleetro- 
magnctic  telegraph. 

Thi.s  beautiful  thing — thi.s  mysterious  telegraj)!) — l>eginning 
awav  off  a  century  ago,  and  now  so  developed  that  man  can 
speak  to  his  fello\\-man  at  the  distance  of  hundreds  of  miles,  as 
though  they  were  face  to  face,  and  can  h(>ar  the  tones  of  tlie 
familiar  A^oice,  and  the  loved  accent,  of  him  whom  he  would 
Avish  to  greet — that  beautiful  thing  has  been  created  by  the 
genius  and  the  eflorts  of  numbers  of  oui'  fellow-men,  whose 
names  ought  to  be  remembered  now.  Franklin,  Oersted,  Arago, 
Amii6re,  Davy,  Sturgeon,  Ilein-y,  Page  and  Gray  (who  also  in- 
vented the  iir.st  articulating  telephone),  are  they  who  made  the 
great  u;'-coverie.s,  and  added  to  theti'ea.sury  of  human  knowledge 
the  truths  upon  which  these  wonderful  and  beautiful  results 
are  jiroduccd.  Passing  by  them,  and  coming  to  ihc  men  who 
made  the  new  combinatiouH  <;f  mechanical  devices,  to  utilize 
those  discoveries,  w(^  have  in  order — Morse,  Cooke,  Steiidieil, 
lieiss,  Stearns,  Edison,  Bell,  Dolbear — all  names  worthy  t)f 
lienor  and  respect.  '^^IMie  first  arc  investigators  in  .science,  who 
have  discovered  new  trutlus — who  have  ascended  from  nature 
to  nature's  God — who  have  traced  out  some  of  the  secret  links 
that  bind  together  liumanity  an(i  the  Supreme  Being  in  one 
common  chain ;  the  others  are  men  who  have,  by  their  ingcnuit}' 
and  mechanical  skill,  developed  these  discoveries  into  usefulne,s.s, 
niniv  jiiiil  more  perfect,  for  man.  Let  us  think  of  them,  and 
be  thankful  to  them,  for  what  tluy  have  done  for  u.s.  Then- 
names  are  for  ever  as,soeiated  witli  this  izreat  art,  under  which 


VI 


IXTKODUCTION. 


SO  much  advance  has  been  made  in  civilization,  in  refinement, 
and  in  love  among  men — so  much  has  been  done  to  dispel  the 
dark  clouds  of  war  from  earth,  and  make  us  all  one  oonimon 
family — the  brotherhood  of  man. 

Along  the  amootli  and  slender  wires 

The  sleepless  lieridds  run, 
Fast  as  tlio  clear  and  living  riiys 

Go  streaming  from  the  sun. 
No  peals  or  flashes,  heard  or  seen, 

Their  wondrous  flight  betray; 
But  yet  their  words  are  quickly  felt 

In  cities  far  away. 


Nor  summer's  heat,  nor  winter's  cold. 

Can  check  their  rapid  course ; 
Unmoved  tlicy  meet  the  fierce  v.-ind's  Ijlast — 

The  rough  waves'  sweeping  force. 
In  the  long  night  of  rain  and  wratli. 

As  in  the  blaze  of  day, 
Tlioy  rusli,  with  news  nf  weal  or  woo 

To  thousands  far  away. 


'^. 


CHAPTER!    H.M,Pomeroy,M,D. 
THE  SPEAKIxa  TELEl'HON*li:°^  Angeles,  Cal. 

The  Speaking  Telephone,  a  recent  American  invention,  which 
at  the  present  moment  is  exciting  the  wonder  and  admiration  of 
the  civilized  world,  is  a  device  for  transmitting  to  a  distance, 
over  an  electric  circuit,  and  accurately  reproducing  at  any  desired 
place,  various  kinds  of  sounds,  including  those  of  the  human 
voice.  The  function  of  the  telephone  is  analogous  to  that  of 
a  speaking  tube  capable  of  almost  infinite  extension,  through 
which  conversation  may  be  carried  on  as  readily  as  with  per- 
sons in  the  same  room. 

Before  proceeding  to  give  a  description  of  the  apparatus 
employed  for  communicating  or  reproducing  articulate  sjieech  at 
a  distance  by  the  telephone,  it  will  be  well  to  devote  some  con- 
sideration to  the  process  by  which  the  ear  distinguishes  the  vibra- 
tions of  a  particular  tone,  or  the  aggregate  of  the  vibrations  of 
all  the  tones  which  simultaneously  act  upon  it,  for  by  this  means 
we  may  be  enabled  to  ascertain  the  conditions  under  which  the 
transmitting  and  receiving  apparatus  must  act  in  order  to  effect 
the  desired  result. 

It  is  well  known  that  the  sensation  which  we  call  sound  is 
excited  by  the  action  of  the  vibrations  of  the  atmosphere  upon 
the  tympanum  or  drum  of  the  ear,  and  that  these  vibrations  are 
conveyed  from  the  tympanum  to  the  auricular  nerves  in  the 
interior  parts  of  the  ear,  by  means  of  a  mechanical  apparatus  of 
wonderful  delicacy  and  precision  of  action,  consisting  of  a  series 
ot"  bones  termed  respectively  the  hammer,  anvil  and  stirrup.  In 
the  process  of  reproducing  tones  by  electro-magnetism,  an  arti- 
ficial imitation  of  the  mechanism  of  the  human  ear  is  emi)loyed, 
consisting  of  a  stretched  membrane  or  diaphragm  corresponding 
to  the  tympanum,  which  by  its  vibrations  generates  and  controls 


6 


THE    SPEAKIXG    TELKPHONE. 


an  electric  circuit  extended  lo  ii  distant  station  by  a,  metallic 
conductor. 

If  we  analyze  the  process  by  which  the  ear  distinguishes  a 
simple  sound,  we  find  that  a  tone  results  from  the  alternate  ex- 
pansion and  condensation  of  an  clastic  medium.  If  this  jirocess 
takes  place  in  the  medium  in  which  the  car  is  situated,  namely, 
the  atmosphere,  then  at  each  recurring  condensation  the  elastic 
membrane  or  tymjianum  will  be  pressed  inward,  and  these  vibra- 
tions will  be  transmitted,  by  the  mechanism  above  referred  to,  to 
the  auricular  nerves. 

The  greater  the  degree  of  condensation  of  the  elastic  medium 
in  a  given  time,  the  greater  is  the  amplitude  of  the  movement  of 
the  tympanum,  and  consequently  of  the  mcclianism  which  acts 
v.pon  the  nerves.  He:.ce  it  follows  that  the  function  of  the 
human  ear  is  the  mechanical  transmission  to  the  auditory  nerves 
of  each  expansion  and  contraction  which  occiu's  in  the  surround- 
ing medium,  while  that  of  the  nerves  is  to  convey  to  the  brain 
the  sensations  thus  produced.  A  scries  of  vibrations,  a  detinite 
number  of  ■v.  iiich  are  produced  in  a  given  time,  and  of  which  we 
thus  become  cognizant,  is  called  a  tone. 

The  action  which  has  thus  reached  our  consciousness,  being  a 
purely  mechanical  one,  may  be  rendered  much  more  easy  of 
comprehension  by  graphical  delineation.  If,  for  example,  we 
assume  the  horizontal  line  a  h  to  represent  a  certain  period  of 
time,  let  the  curves  extending  above  the  line  (f  h  rejiresent  the 


successive  condensations  (  -f- ),  nnd  the  ciu'ves  below  the  lino  the 
successive  expansions  ( — ),  then  each  ordinate  represents  the 
degree  of  condensation  or  expansion  at  tlie  moment  of  time  cor- 
responding to  its  position  upon  the  linea  //  and  also  the  amplitude 
of  the  vibrations  of  the  tympanum. 

A  simple  musical  tone  results  from  a  continuous,  rapid  and 
uniformly  recurring  series  of  vibrations,  provided  the  number  of 


THE   CHARACTERISTICS    OF   SOfND. 


7 


complete  vibrations  per  second  falls  within  certain  limits.  If, 
lor  example,  the  vibrations  number  less  than  seven  or  eight  per 
second,  a  series  of  successive  noises  are  heard  instead  of  a  tone, 
while  if  their  number  exceeds  forty  thousand  per  second,  the 
ear  becomes  incapable  of  appreciating  the  sound. 

The  ear  distinguishes  three  distinct  characteristics  of  sound : 

1.  The  tone  or  pitch,  by  virtue  of  whicli  sounds  are  high  or 
low,  and  which  depends  upon  the  rapidity  of  the  vilmatory  move- 
ment The  more  rapid  the  vibrations  the  more  acute  will  bo  the 
sound. 

2.  The  intensity,  by  virtue  of  which  sounds  are  loud  or  soft, 
and  which  depends  upon  the  amplitude  of  the  vibrations. 

3.  The  quality,  by  which  we  are  able  to  distinguish  a  note 
sounded  upon,  for  example,  a  violin,  from  the  same  note 
when  sounded  upon  a  flute.  By  a  remarkable  series  of  experi- 
mental investigations  Ilelmholtz  succeeded  in  demonstrating 
that  the  different  qualities  of  sounds  depend  altogether  upon  the 
number  and  intensity  of  the  overtones  which  accompany  the 
primary  tones  of  those  sounds.  The  different  characteristics  of 
sound  may  be  graphically  represented  and  the  phenomena  thus 
rendered  more  easy  of  comprehension. 

In  lig.  1,  for  example,  let  the  lines  c  8  represent  a  certain 
length  of  time,  and  the  continuous  curved  line  the  successive 
vibrations  producing  a  simple  tone.  The  curves  above  the  line 
represent  the  compression  of  the  air,  and  those  below  the  line 
its  rarefaction ;  the  air,  an  elastic  medium,  is  thus  thrown  into 
vibrations  which  transmit  the  sound  waves  to  the  ear.  The  ear 
is  unable  to  appreoiai.  any  sensations  of  sound  other  than  those 
produced  by  vibrations,  which  may  be  represented  by  curves 
similar  to  that  above  described.  Even  if  several  tones  are  pro- 
duced simultaneously,  the  elastic  medium  of  transmission  is 
under  the  influence  of  several  forces  acting  at  the  san.e  time, 
and  which  are  subject  to  the  ordinary  laws  of  mechanics.  If  the 
diff'irent  forces  act  in  the  same  direction  the  total  force  is  rep- 
resented by  their  sum,  while  if  they  act  in  opposite  directions,  it 
is  represented  by  the  difference  between  them. 


8 


THE   SPEAKING  TELEPHONE. 


Ill  fig.  1  three  distinct  simple  tones,  c,  g  and  e  are  represented, 
the  rapidity  of  the  vibrations  being  in  the  proportion  of  8,  6 
and  5.  The  composite  tone  resulting  from  the  simultaneous  pro- 
duction of  the  tln-ee  simple  tones  is  represented  graphically  by 
the  fourth  line,  which  correctly  exhibits  to  the  eye  the  effect  pro- 


Pigs.  ^,  2,  3. 

duced  u})on  tlie  ear  by  the  three  simultaneously  acting  simple 
tones. 

Fig.  2  represents  a  curve  formed  of  more  than  three  tones, 
in  which  the  relations  do  not  appear  so  distinctly,  but  a  musical 


ItEISSS  MUSIOAL  TELEPHONE. 


9 


expert  will  readily  recognize  them,  even  when  it  would  be  diffi- 
cult in  practice  for  him  to  distinguish  the  simple  tones  in  such  a 
chord. 

This  method  of  showing  the  action  of  tones  u[)on  the  human 
ear  possesses  the  advantage  of  giving  the  clearest  illustration 
possible  of  the  entire  process. 

We  may  even  understand  by  reference  to  fig.  3  why  it  is  that 
the  car  is  so  disagreeably  affected  by  a  discord. 

It  will  be  observed  that  the  curves  in  the  diagram  represent 
the  three  characteristics  of  sound  which  have  been  referred  to. 
The  pitch  is  denoted  by  the  number  of  vibrations  or  waves  re- 
curring within  a  given  horizontal  distance ;  the  intensity  by 
the  amj^litudc  of  the  vibrations — that  is  their  comparative 
height  above  or  depth  below  the  horizontal  line — and  the 
quality  I'y  the  form  of  the  waves  themselves.  It  is,  therefore, 
easy  to  understand  that  if,  by  any  means  whatever,  we  can  pro- 
duce viVjrations  whose  curves  correspond  to  those  of  a  giv'^ 
tone  or  a  given  combination  of  tones,  the  same  impression  will  be 
produced  upon  the  ear  that  would  have  been  produced  by  the 
original  tone,  whether  simple  or  composita 

The  earliest  experiments  in  the  production  of  musical  sounds 
at  a  distance,  by  means  of  electro-magnetism,  appear  to  have 
been  made  in  1861  by  Philip  Reiss,  of  Friedrichsdorf,  Germany. 
Ilis  apparatus  was  constructed  in  the  manner  shown  in  fig.  4. 

A  is  the  transmitting  and  B  the  receiving  apparatus,  which 
arc  supposed  to  be  situated  at  different  stations.  For  the  sake  of 
clearness,  the  appliances  by  which  the  apparatus  is  arranged  for 
reciprocal  transmission  in  one  direction  or  the  other  have  been 
omitted.  Furthermore,  it  may  be  well  to  state  that,  as  the  ap- 
paratus was  constructed  merely  for  tlie  purpose  of  making  known 
to  a  wider  circle  the  discoveries  which  had  thus  flxr  been  made, 
the  possibility  of  extending  the  action  of  the  apparatus  to  a  dis- 
tance beyond  the  limit  of  the  direct  action  of  the  current  had  not 
been  taken  into  consideration.  This  is  a  mere  question  of  me- 
chanical construction,  and  has  no  especial  bearing  upon  the  phe- 
nomena under  consideration.     The  tone  transmitter  A,  figure  4, 


10 


THE  SPEAKING  TELEI'HONK. 


is  on  tlio  ono  liand  coniiectnd  bj  a  metallic  conductor  with  the 
tone  receiver  15  at  the  distant  station,  and  on  the  other  with  the 
battery  C'  and  the  earth,  or  the  return  conductor.     It  consists  of 


a  conical  tube,  a  b,  about  6  inches  in  length,  and  having  a  di- 
ameter of  4  inches  at  the  larger  and  1^  inches  at  the  smaller  end. 


HEISS.S   MUSICATi   TELEPnONK. 


11 


with  tlie 
witli  the 
onsists  of 


r 


laving  a  di- 
maller  end. 


It,  was  found  by  experiment  that  the  material  of  wliich  the  tube 
was  constructed  had  no  influence  upon  tlie  action  of  the  appa- 
ratus, and  the  same  is  true  as  to  its  lengtli.  An  increase  in  the 
diameter  of  the  tube  was  found  to  impair  the  elFect,  The  inner 
surface  of  the  tube  should  be  made  as  smootli  as  possible.  The 
smaller  or  rear  end  of  the  tube  ia  closed  by  means  of  a  collodion 
membrane,  o,  against  the  centre  of  wliich  rests  one  extremity,  c, 
of  the  lever  c  d,  which  lever  is  in  electrical  connection  with  the 
metallic  conducting  wire  through  its  point  e  and  supporting 
bracket.  The  proper  length  and  proportion  to  be  given  to  the 
respective  arms  c  o  and  rf  e  of  the  lever  c  e  d  ia  determined  by 
mechanical  considerations.  It  is  advisable  that  the  length  of  the 
arm  c  e  should  be  greater  than  that  of  d  e,  so  as  to  produce  the 
necessary  movement  at  c  with  the  least  possible  exertion  of 
force  at  d.  The  lever  itself  should  be  made  as  light  as  possible, 
in  order  that  it  may  follow  with  certainty  the  movements  of  the 
membrane,  as  any  inaccuracy  in  tliis  respect  will  give  rise  to  a 
false  tone  at  the  receiving  station.  When  the  apparatus  is  in  a 
state  of  rest  the  contact  at  d  ^  is  closed ;  a  delicate  spring  n 
maintains  the  lever  in  this  j^osition.  The  metallic  standard  /  is 
connected  with  one  pole  of  the  battery  C,  the  other  pole  of  which 
is  connected  to  the  earth,  or  to  the  return  wire  leading  to  the 
other  station.  A  flat  si)ring  g  is  attached  to  the  standard  f,  and 
is  provided  with  a  contact  point  corresponding  to  that  at  d  upon 
the  lever  c  d.  The  position  of  this  contact  point  may  be  adjusted 
by  means  of  a  screw  h. 

In  order  to  prevent  the  interference  occasioned  by  the  action 
of  the  sonorous  vibrations  of  the  atmosphere  upon  the  back  side 
of  the  membrane,  when  making  use  of  the  apparatus,  it  is  advis- 
able to  place  a  disk  about  twenty  inches  in  diameter  upon  the 
tube  o  b,  in  the  form  of  a  collar  or  flange,  at  right  angles  to  its 
longitudinal  axis. 

The  tone  receiver  B,  fig.  4,  consists  of  an  electro-magnet  m, 
mounted  upon  a  sounding  box  or  resonator  lo,  and  included  in 
tlie  circuit  of  the  electrical  conductor  from  the  transmitting 
station.     Facing  the  poles  of  the  electro-magnet  is  an  armature 


12 


THE   SPEAKING  TELEPHONE. 


which  is  attached  to  a  broad  but  thin  and  light  plate,  i,  which 
should  be  made  as  long  as  possible.  The  lever  and  armature 
are  suspended  from  the  upright  support  k,  in  the  manner  of  a 
pendulum,  its  motion  being  regulated  by  tlie  adjusting  screw  I 
and  the  spring  a. 

In  order  to  increase  the  volume  of  sound,  the  tone  receiver 
may  be  placed  at  one  of  the  focal  points  of  an  elliptical  chamber 
of  suitable  size,  while  the  ear  of  the  listener  is  placed  at  the 
other  focal  point 

The  operation  of  the  apparatus  is  as  follows :  When  the 
different  parts  are  in  a  state  of  rest  the  electric  circuit  is  closed. 
If  an  alternate  condensation  and  rarefaction  of  the  air  in  the 
tube  a  6  is  produced  by  speaking,  singing,  or  playing  upon 
a  musical  instrument,  a  corresponding  motion  is  communicaied 
to  the  membrane,  and  from  thence  to  the  lever  e  d,  by  which 
means  the  electric  circuit  is  alternately  opened  and  closed  at  d  g, 
each  condensation  of  the  air  in  the  tube  causing  the  circuit  to 
be  broken,  and  each  rarefaction  in  like  manner  causing  it  to  be 
closed.  Thus  the  electro-magnet  m  m,  of  the  apparatus  at  B, 
becomes  demagnetized  or  magnetized,  according  to  the  alternate 
condensations  and  rarefactions  of  the  body  of  air  contained  in 
the  tube  a  b,  and  consequently  the  armature  of  the  electro-mag- 
net is  thrown  into  vibrations  corresponding  to  those  of  the  mem- 
brane in  the  transmitting  apparatus.  The  plate  t,  to  which  the 
armature  is  attached,  transmits  the  vibrations  of  the  latter  to  the 
surrounding  atmosphere,  which  in  turn  conveys  them  to  the 
ear  of  tlie  listener. 

It  must  however  le  admitted,  that  while  the  apparatus  which 
has  been  described  re^Toduces  the  original  vibrations  with  per- 
fect fidelity,  so  far  as  thei-  number  and  interval  is  concerned,  it 
cannot  transmit  their  intensity  or  amplitude.  The  accomplish- 
ment of  this  latter  result  had  to  await  the  further  development 
of  the  invention. 

It  was  in  consequence  of  this  defect  in  the  apparatus  that  the 
more  inconsiderable  differences  of  the  original  vibrations  were 
distinguished  with  great  difficulty — that  is  to  say,  the  vowel 


HKI3SS   MUSrCAIi  TELEPirONK 


18 


sounds  were  heard  with  moro  or  loss  iiidisiiiictness,  for  the 
reason  that  tho  character  of  each  tone  depends  not  merely  upon 
the  number  of  tho  sonorous  vibrations,  but  upon  their  intensity 
or  amplitude  also.  Tins  also  accounts  for  tho  observed  fact  that 
while  chords  and  melodies  were  transmitted  and  reproduced  with 
a  surprising  degree  of  accuracy,  single  words,  as  pronounced  in 
reading  or  speaking,  were  but  indistinctly  heard,  althougli  in 
this  case,  also,  tho  infl  i.tionsof  the  voice,  interrogative,  exclama- 
tory, etc.,  could  be  distinguished  without  difficulty. 

Figure  5  illustrates  another  form  of  Reiss's  apparatus. 

A  is  a  hollcnv  wooden  box,  provided  with  two  apertures,  one 
at  tlie  top  and  tlio  other  iu  front  The  former  is  covered  with  a 
membrane  S,  such  as  a  piece  of  bladder,  tightly  stretched  in  a 


Fig.  5. 

circular  frame.  When  a  person  sings  into  the  mouthpiece  Af, 
which  is  inserted  in  the  front  opening,  the  whole  force  of  his 
voice  is  concentrated  on  tho  tight  membrane,  which  is  thrown 
into  vibrations  corresponding  exactly  with  tho  vibrations  of  tho 
air  produced  by  the  sound  of  the  singing.  A  thin  piece  of  pla- 
tinum is  glued  to  the  '^entre  of  the  membrane  and  connected 
with  the  binding  screw  a,  in  whicli  a  wire  from  the  battery  B  is 
fixed.  Upon  the  membrane  rests  a  little  tripod  c  fg,  of  which 
tlic  feet  e  and /rest  in  metal  cups  upon  the  cu'cular  frame  over 
which  the  skin  is  stretched.  One  of  them,  J\  rests  in  a  mer- 
cury cup  connected  with  tho  binding  screw  h.  The  third  foot,  r/, 
consisting  of  a  platinum  contact  point,  lies  on  the  strip  of  plati- 


u 


TilK  SPEAKING  TELKl'HONK. 


iiiim  wliich  is  plncod  upon  tlio  ccntro  of  tlm  vibrating  mrmhrnne 
ami  hops  up  and  down  with  it.  By  this  inoans  tiiu  closed  circiiii 
which  passes  tlirough  tho  aj)paratus  from  <t  to  b  is  momentarily 
hroken  for  every  vibration  of  tlic  membrane.  Tlie  receiving 
instrument  R  consists  of  a  coil  or  helix,  enclosing  an  iron  rod 
and  lixod  ujion  a  hollow  sounding  box,  and  is  founded  on  the 
fact,  first  investigated  by  Professor  Joseph  Ilenry,  that  iron  bars, 
when  magnetized  by  means  of  an  electric  current,  become 
.slightly  elongated,  .and  at  the  interruption  oC  tho  current  are  re- 
.stored  to  their  normal  length.  In  the  receiving  instrument  these 
elongations  and  shortenings  of  the  iron  bar  will  succeed  each 
other  with  precisely  tho  .same  interval  as  the  vibrations  of  the 
origin.al  tone,  and  the  longitudinal  vibrations  of  the  bar  will  1)0 
communicated  to  the  sounding  box,  thus  being  made  distinctly 
audible  at  the  receiving  station. 

It  will  be  seen  that  the  result  produced  by  these  devices  i3 
not  the  veritable  transmission  of  sound  by  means  of  the  electric 
current,  but  is  .simply  a  reproduction  of  the  tones  at  .sotno  other 
point,  by  setting  in  action  at  this  jjoint  a  similar  cause,  and 
thereby  i)roducing  a  similar  eilect 

It  is  obvious  that  this  apparatus,  like  the  one  previously  de- 
scribed, is  capable  of  producing  only  one  of  the  three  charac- 
teristics of  sound,  viz.,  its  pitch.  It  cannot  produce  different 
degrees  of  intensity  or  other  qualities  of  tones,  but  merely  sings 
the  melodies  transmitted  with  its  own  voice,  which  is  not  very 
unlike  that  of  a  toy  trumpet.  Referring  to  the  graphic  repre- 
sentation of  the  composite  tone  in  lig.  1,  this  apparatus  would 
reproduce  the  waves  at  properly  recurring  intervals,  but  they 
would  all  be  of  precisely  tho  .same  amplitude  or  intensity,  for 
the  reason  that  they  arc  all  produced  by  an  electric  current  of 
the  same  strength. 

Ill  the  spring  of  1874  Mr.  Elisha  Gray,  r "  Chicago,  invented 
a  method  of  electrical  transmission  by  nicans  of  which  the  in- 
tensity of  the  tone.s,  cas  well  as  their  pitch,  was  properly  repro- 
duced at  the  receiving  station.  This  was  a  very  important  dis- 
covery— in  fact,  an  essential  prerequisite  to  the  development  of 


gray's  Sl'KAKINO  TELEl'lIONE. 


16 


tbo  teloplione,  both  n  respect  to  tlio  reproduction  of  liannonic 
.•nuHicul  tones  iind  of  articulate  speech,  as  it  enabled  any  required 
iiunibcr  of  dilTcrcut  tones  to  be  reproduced  simultaneously  with- 
out destroyinf^  their  individuality. 

In  this  method  the  transmitters  were  so  arranged  that  a  sepa- 
rate series  of  electrical  impulses  of  varying  strength  as  well  as 
rapidity  ])asscd  into  the  line,  thus  reproducing  at  the  distant  end 
tiie  intensities  of  tlie  vibrations,  corresponding  to  the  graphic 
r<4)rcsentiition  on  the  fourth  or  ])ottom  line  of  fig.  1.  By 
tliis  means  a  tuno  could  be  reproduced  at  any  disUmce  with 
perfect  accuracy,  including  its  pitch  and  varying  intensity  as 
well  as  (piidity  of  sound.      With  a  receiving  in.strument  consist- 


TTUT 


H(/.  r,. 

ing  of  an  electro-magnet,  having  its  armature  rigidly  fixed  to 
one  pole,  and  separated  from  the  other  by  a  space  of  -j'^-  of  an 
inch,  and  mounted  upon  a  hollow  sounding  box,  which,  like  that 
of  a  violin,  responded  to  all  vibrations  which  were  communicated 
to  it,  the  tones  became  very  loud  and  distinct 

Subsequently  Mr.  Gray  conceived  the  idea  of  controlling  the 
formation  of  what  may  be  termed  tlie  electric  waves,  as  repre- 
sented in  the  diagram,  figs.  1,  2  and  3,  by  means  of  the  vibra- 
tions of  a  diaphragm  capable  of  responding  to  sounds  of  ever}' 
kind  traversing  the  atmosphere,  so  arranged  as  to  reprodiice 
these  vibrations  at  a  distance.  When  this  was  ac<'ompli.shed,  the 
])r()blem  of  the  transmission  and  reproduction  of  articulate  speech 
over  an  electric  conductor  was  theoretically  solved. 


16 


THE   SPEAKING   TELEPHONE. 


Tlie  principle  and  mode  of  operation  ot  Gray's  original 
telephone  are  shown  in  the  accompanying  fig.  6.  '^i'he  per- 
son transmitting  sounds  sjieaks  into  tlie  niontlipiece  T^.  D' 
is  a  diaphragm  of  some  tliin  substance  capable  of  respond- 
ing to  the  various  complex  vibrations  produced  by  the  human 
voice.  To  the  centre  of  the  diaphragm  one  end  of  a  light  metallic 
rod,  N,  is  rigidly  attached,  the  other  cxtemding  into  a  glass  vessel 
J,  placed  beneath  the  chamber.  This  vessel,  wliose  lower  end  is 
closed  by  a  metallic  plug,  P,  is  filled  with  sliglitly  acidulated 
water,  or  some  other  liquid  of  the  same  specific  resistance,  and 
the  metallic  plug  or  end  placed  in  connection  with  one  terminal 
of  an  electric  circuit,  the  other  end  being  joined  b}^  a  very  light 
wire  to  tlie  rod  N,  near  the  diaphragm.  It  will  thus  be  seen 
that  the  water  in  the  vessel  forms  a  ])art  of  the  circuit  through 
which  tlie  current  from  a  battery  placed  in  this  circuit  will  pass. 
Now,  as  the  excursions  of  the  plunger  rod  vary  witli  the  ampli- 
tude of  tlie  several  vibrations  made  by  the  diaphragm  to  wliich 
it  is  attached,  as  well  as  with  the  rapidity  of  their  succession,  it 
will  readih'  be  seen  that  the  distance,  and  consequently  the  resist- 
ance to  the  passage  of  tlie  current,  between  the  lower  end  of  the 
rod  and  the  metallic  l)lug,  must  vary  in  a  similar  manner,  and 
this  produces  a  series  of  corresponding  variations  in  the  strength 
of  the  battery  current. 

Tlie  receiving  ajiparatus  consists  simply  of  an  electro-magnet, 
H,  and  armature,  a  diaphragm,  D,  and  a  mouthpiece,  T.  Tlie 
soft  iron  armature  which  is  attached  to  the  diaphragm  stands 
just  in  front  of  the  electromagnet;  consequently,  when  the 
latter  acts,  it  does  so  in  obedience  to  current  pulsations,  wlii(;li 
have  all  the  cliaracteristics  of  the  vibrating  diaphi'agm  D,  and 
thus,  tlirough  the  additional  intermediary  of  tlie  soft  iron,  the 
vibrations  produced  by  the  voice  in  T  are  communicated  to  tlie 
diaphragm  T  of  the  receiving  a[)paratus,  and  thus  sounds  of 
every  character,  including  all  the  ionaa  of  tlie  Inmian  voice,  are 
reproduced  with  absolute  fidelity  and  distinctness. 

In  the  summer  of  1876  Professor  A.  G.  Bell,  of  the  Boston 
University,  exhibited  at  the  Centennial  Exhibition,  in  Phila- 


BELLS  SPEAKING  TELEPHONE. 


17 


delphia,  a  telephonic  apparatus,  differing  somewhat  in  its  details 
from  that  just  described,  by  which  articulate  speech  could  be 
transmitted  over  an  electric  circuit,  and  reproduced  at  a  distance 
with  some  degree  of  distinctness. 

The  princii)le  of  his  method  is  illustrated  in  fig.  7.  A  repre- 
sents the  transmitting  and  B  the  receiving  apparatus.  When 
a  ])erson  speaks  in'o  the  tube  T,  in  the  direction  of  the  arrow, 
the  acoustic  vibrations  of  the  air  are  communicated  to  a  mem- 
brane tightly  stretched  across  the  end.  of  the  tube,  upon  which 
is  cemented  a  light  permanent  bar  magnet  ?i  s.  Tliis  is  in 
close  proximity  to  the  poles  of  an  electro-magnet  M,  in  the 
circuit  of  the  line,  which  is  constantly  charged  by  a  current 
from  the  battery  E.     The  vibrations  of  the  magnet  n  s  induce 


D 


F(j.  7. 


magne*-c-electric  pulsations  in  the  coils  of  the  electro-magnet  M, 
which  traver.-e  the  circuit,  and  the  inagi'itude  oi.  the^e  pulsa- 
tions is  proportional  to  the  rajudity  and  amplitude  of  the  vibra- 
tions of  the  magnet;  thus,  for  instance,  when  the  small  perma- 
nent magnet  is  made  to  move  towanl  M,  a  current  of  electricity 
will  be  induced  in  the  coils,  'vhich  will  traverse  the  whole  cir-. 
cuit.  This  induced  electricity  will  consist  of  a  single  wave  or 
pulse,  and  its  force  will  depend  upon  the  velocity  of  the  ap- 
|iroach  of  n  s  to  M.  A  like  pulse  of  electricity  will  be  induced 
in  tiio  coils  when  n  s  is  made  to  move  away  from  M ;  but  this 
current  will  move  through  the  circuit  in  an  opposite  direction, 
so  that  whether  the  pul.sation  goes  from  A  t  >  B  or  from  B  to  A, 
depends  simply  upon  the  direction  of  the  motion  of  n  5. 


18 


THE  SPEAKING  TELEPHONE. 


The  electricity  thus  generated  in  the  wire  by  such  vibratory 
movements  varies  in  strength,  as  already  observed,  with  the 
variations  in  the  movement  of  the  armature  ;  the  line  wire  be- 
tween two  places  will,  therefore,  be  filled  with  electrical  pulsa- 
tions exactly  like  the  atrial  pulsations  in  structure. 

These  induced  electric  currents  are  very  trnnsient,  and  their 
effect  upon  the  receiver  R  is  either  to  increase  or  decrease  the 
power  of  the  magnet  there,  as  they  are  in  one  direction  or  the 
other,  and  consequently  to  vary  the  nttractive  power  exercised 
upon  the  iron  plate  armature. 

Let  a  simple  sound  be  made  in  the  tube,  consisting  of  256 
vibrations  per  second ;  the  membrane  carrying  the  iron  will 
vibrate  as  many  times,  and  so  many  pulses  of  induced  elec- 
tricity will  be  imposed  upon  the  constant  current,  which  will 
each  act  upon  the  receiver,  and  cause  so  many  vibrations  of  the 
armature  upon  it;  and  an  ear  held  near  /•  will  hear  the  sound 
with  the  same  pitch  as  that  at  the  sending  instrument  If  two 
or  more  sound  waves  act  simultaneously  upon  the  membrane, 
its  motions  must  correspond  with  such  combined  motion  ;  that 
is,  its  motion  will  be  the  resultant  of  all  the  sound  waves,  and 
the  corresponding  pulsations  in  the  current  must  reproduce  at 
B  the  same  eflect.  Now,  when  a  person  speaks  in  the  tube,  the 
membrane  is  thrown  into  vibrations  more  complex  in  structure 
than  those  just  mentioneil,  differing  only  in  number  and  inten- 
sity. The  magnet  will  cause  responses  from  even  the  minut- 
est motion,  and,  therefore,  an  ear  near  r  will  hear  what  is 
said  in  the  tube.  Consequently,  this  apparatus  is  capable  of 
transmitting  ^:Dth  the  pitch  and  intensity  of  the  tones  which  enter 
the  tube  T.  The  receiving  instrument  consists  simply  of  a 
tubular  electro-magnet  R,  formed  of  a  single  helix  with  an  ex- 
ternal soft  iron  casi',  into  the  top  of  whif;h  is  loosely  fitted  the 
iron  plate  r,  which  is  thrown  into  vibrations  by  the  action  of 
the  magnetizing  helix.  The  sounds  produced  in  this  manne 
were  quite  weak,  and  could  be  transmitted  but  a  short  distance ; 
but  the  mere  accomplisiiment  of  the  feat  of  transmitting  electric 
impulses  over  a  metallic  wire  which  should  reproduce  articu- 


DOLBEARS  SPKAKING  TELEPHONE. 


19 


late  speech,  even  in  an  imperfect  manner,  at  the  farther  end,  ex- 
cited great  interest  in  a  scientific  as  well  as  jiopular  point  of 
view,  throughout  the  civilized  world. 

During  the  ensuing  autumn  some  important  changes  in  the 
telephone  were  effected,  wherel)y  its  articulating  properties 
were  greatly  improved.  Professor  A.  E.  Dolbear,  of  Tufts  Col- 
lege, observing  that  the  actual  function  of  the  battery  current 
with  which  the  line  was  charged  in  Bell's  method  had  simply 
the  effect  oi  polarizing  the  soft  iron  cores  of  the  transmitting  and 
receiving  instruments,  or  of  converting  them  into  permanent 
magnets,  and  that  the  mere  passage  of  the  constant  voltaic  cur- 
rent over  the  line  had  nothing  to  do  with  the  result,  conceived 
the  idea  of  maintaining  the  cores  in  a  permanently  magnetic  or 
polarized  state  by  the  inductive  influence  of  a  permanent  mag- 


^ 


net  instead  of  by  a  voltaic  current.  He  therefore  substituted 
])crmanent  magnets  with  small  helices  of  insulated  copper  wire 
surrounding  one  or  both  poles,  in  place  of  the  electro-magnets 
and  battery  previously  employed. 

Another  important  improvement  made  by  him  consisted  in 
using  the  same  instrument  for  botli  sending  and  receiving  instead 
of  employing  instruments  of  different  construction,  as  all  previous 
inventors  han  done. 

The  principle  and  mode  of  operation  of  the  improved  appara- 
tus is  represented  in  figure  8. 

It  consists  of  an  ordinary  permanent  bar  magnet,  N  S,  a  single 
helix,  n,  of  insulated  copper  wire  placed  upon  one  end  of  the 
magnet,  and  a  metallic  diaphragm,  D,  consisting  of  a  disk  of  thin 


20 


THE   SPEAKING   TELEPHONE. 


sheet  iron,  two  and  a  quarter  inches  in  diiimctcr  and  one  fiftieth 
of  an  inch  thick,  forming  an  armature  to  the  magnet,  N  S.  The 
vibratory  motions  of  the  air  produced  by  the  voice  or  other 
cause  are  directed  towards  and  concentratctl  u})ou  the  diaphragm, 
D,  by  means  of  a  mouthpiece,  T.  It  will  thus  be  seen  that  when 
vibrations  are  communicated  to  the  air  in  front  of  the  mouth- 
piece the  impact  of  the  waves  of  air  against  the  elastic  dia{>lu'agm 
will  cause  a  corresponding  movement  of  the  latter.  This  in  turn, 
by  reacting  upon  the  magnet,  disturbs  the  normal  magnetic  con- 
dition of  the  bar,  and  since  any  change  of  magnetism  in  this 
tends  to  generate  electrical  currents  in  the  surrounding  helix,  the 
circuit  in  which  the  helix  may  be  placed  will  be  traversed  by  a 
series  of  electrical  pulsations  or  currents.  Moreover,  as  these 
currents  continue  to  be  generated  to  long  as  the  niotion  of  the 
diaphragm  continues,  and  as  they  increase  and  decrease  in 
strength  with  the  amplitude  of  its  vibrations,  thus  varying  with 
the  variations  of  its  amplitude,  it  is  evident  that  they  virtually 
possess  all  the  physical  characteristics  of  the  agent  acting  upon 
the  transmitting  diaphragm.  Consequently,  by  their  electro- 
magnetic action  upon  the  magnet  of  an  apparatus  identical  with 
the  one  above  described,  and  placed  in  the  same  circuit  at  the 
receiving  end,  they  will  cause  its  diaphragm  to  vibrate  in  exact 
correspondence  with  that  of  the  transmitting  apparatus.  ' 

During  the  past  year  many  ingenious  persons  have  turned  their 
attention  to  the  subject  of  telephones,  and  by  the  introduction 
of  various  modifications  have  succeeded  in  greatly  improving 
the  invention,  so  as  to  make  it  available  for  practical  applica- 
tion. Prominent  among  these  is  ^fr.  G.  M.  Phelps,  mechunician 
of  the  Western  Union  Telegraph  Company,  to  whose  ability  in 
the  invention  of  valuable  improvements,  as  well  as  in  the  scien- 
tific arrangement  of  details  in  tlie  construction  of  the  apparatus, 
the  public  is  indebted  for  some  of  the  most  eflective  telephones 
yet  introduced.  Tiie  peculiar  excellence  of  these  instruments 
consists  in  their  distinct  articulation,  combined  with  a  loudness 
of  utterance  that  is  not  often  met  with  in  the  numerous  other 
forms  that  have  appeared  up  to  the  present  time.     Both  of  these 


PHELPS  S   DUPLEX   TELEPHONE, 


21 


qualities,  manifestly  so  desirable,  are  developed  in  these  instru- 
ments in  a  very  remarkable  degree,  while  the  distance  over  which 
they  may  be  used  is  also  another  of  their  distinguishing  charac- 
teristics, circuits  of  over  one  hundred  miles  having  been  worked 
by  them  with  the  most  admirable  results. 

The  most  essential  improvements  introduced  by  Mr.  Phelps 
consist  in  combining  two  or  more  vibrating  diaphragms  and  two 
or  more  corresponding  magnetic  cores,  enveloped  in  separate 
helices,  connected  in  the  same  circuit,  with  a  single  mouthpiece 
or  vocalizing  chamber  ;  in  mounting  two  magnetic  cores,  when 
combined  with  separate  diaphragms  and  coils,  and  a  single 
mouthpiece,  upon  opposite  poles  of  the  same  permanent  magnet, 


ami  in  subdividing  a  single  continuous  induction  plate  into  two 
or  more  separate  and  distinct  areas  of  vibration,  thus  virtually 
forming  two  or  more  separate  diaphragms,  each  of  which  acts  or 
is  acted  ui)ou  b\'  a  separate  magnetic  core,  to  the  conseciuent  in- 
creased usefulness  of  the  apparatus. 

Figure  9  represents  a  form  of  the  instrument  constructed 
upon  the  above  principles,  which,  both  as  regards  distinctness  of 
articulation  and  the  facility  with  which  it  permits  conversation 
to  be  carried  on  in  consequence  of  the  loudness  of  its  tone,  leaves 
little  else  to  be  desired.  It  consists  of  the  permanent  magnet  M 
of  hardened  steel,  which  is  bent  into  an  oblong  form,  so  as  to 
occii|iy  but  little  space,  and  also  bring  its  poles  conveniently 
near  each  other  ;  two  helices,  11  and  II',  of  copper  wire,  placed 
respectively  upon  the  north  and  south  poles  of  the  magnet;  two 


22 


THE   SPEAKING  TELEPUONE. 


metallic  diaphragms,  D  and  D*,  and  the  speiiking  tube  or  mouth- 
piece T,  which  may  be  made  of  wood,  metal,  or  suoh  other 
substance  as  fancy  may  suggest.  The  diaphrngms  are  placed 
upon  opposite  sides  of  a  short  cylindrical  piece  of  hard  rubber, 
provided  with  a  lateral  opening  for  the  insertion  of  the  mouth- 
piece, and,  together  with  it,  form  a  sort  of  chamber,  within 
which  the  air  is  alternately  condensed  and  rarefied,  in  conse- 
quence of  the  motion  or  impulses  communicated  to  its  particles 
by  the  voice  when  directed  toward  the  opening  of  the  tube. 
Hence,  it  will  be  seen  that  each  condensation  exerts  an  outward 
pressure  of  its  own  upon  the  diaphragm,  while  ench  rarefaction 
causes  a  corresponding  pressure  from  the  external  air,  and  thus 
a  vibratory  movement  is  imparted  to  both  diaphragms  at  one 
and  the  same  instant ;  consequently,  if  the  helices  are  so  con- 
nected that  the  direction  of  the  current  pulsations,  which  are 
inductively  produced  by  the  vibrations  of  the  diaphragms  in  the 
raanner  already  explained,  are  similar  when  they  become  united 
in  the  line,  the  magnetic  force,  as  exhibited  in  the  receiving  ap- 
paratus at  the  distant  station,  will  be  augmented  considerably 
above  that  produced  by  the  action  of  a  single  coil  and  diaphragm 
alone,  and  thereby  a  corresponding  increase  in  the  loudness  of 
the  sound  will  be  produced.  The  besteirocts  are  obtained  when 
instruments  of  this  form  are  employed  both  in  transmitting  and 
receiving,  the  advantages  they  possess  for  the  latter  purpose 
being  quite  as  marked  as  for  the  former,  as  will  appear  obvious 
enough  when  we  consider  that  every  time  a  current  p:\s.«es 
through  the  helices  tlie  attractive  forces  thereby  imparted  to  the 
cores  or  magnet  poles  are  such  as  to  cause  the  centres  of  the  two 
diaphragms  to  be  drawn  directly  from  eacli  other,  thus  produc- 
ing a  ""  'ch  greater  rarefaction  of  the  air  within  the  chamber 
than  ^^ald  be  obtained  by  the  action  of  a  single  diaphragm 
alone.  A  corresponding  condensation,  on  tlic  other  hand,  is  pro- 
duced at  each  cessation  of  tlie  current,  owing  to  the  return  of  the 
diaphragms,  in  virtue  of  their  elasticity  to  their  normal  position. 
The  greater  the  degree  of  condensation  and  rarefaction,  how- 
ever, the  greater  the  amplitude  of  tlie  sonorous  vibrations — one 


PHELPS  S  DUPLEX  TELEPHONE. 


23 


•r  mouth- 
loli  other 
re  placed 
1  rubber, 
le  mouth- 
:r,  within 
in  conse- 
!  particles 
the  tube. 
I  outward 
arefaction 
and  thus 
;ras  at  one 
re  so  con- 
which  are 
^ms  in  the 
irne  united 
leiving  ap- 
tisidcrably 
liaphragm 
oudness  of 
,ined  when 
litting  and 
!r  purpose 
ar  obvious 
ent   p;\s.«es 
rted  to  the 
of  the  two 
us  produc- 
le  chamber 
diaphragm 
and,  is  pro- 
turn  of  the 
al  position, 
ction,  how- 
itions — one 


expression  being  the  equivalent  of  the  other — and,  therefore,  the 
<'-reater  will  be  the  intensity  or  loudness  of  the  sound  produced. 
We  might  add,  in  this  connection,  that  the  introduction  of  a 
second  helix  in  the  lino  circuits  presents  in  itself  a  slight  disad- 
vantage. This  arises  from  the  inductive  action  of  the  pulsatory 
currents  upon  themselves  in  the  coils  and  the  reactive  influence 
of  the  core,  wliereby  other  and  opposing  currents  are  produced, 
which  tend  to  delay,  and,  in  part,  neutralize  the  effects  of  the 
former.  The  latter  are  termed  extra  currents,  to  distinguish 
them  from  those  produced  in  circuits  exterior  to  that  in  which 


Fi^j.  10. 

tlie  inducing  currents  are  passing.  As  tlicy  are  found  to  accom- 
pany all  electro-magnetic  action  whenever  one  i)art  of  a  circuit 
is  brought  in  proximity  to  another,  as  is  the  ca-^e  in  magnet 
helices,  it  will  readily  be  seen  that  they  must  become  the  more 
troublesome  as  the  number  of  stations  are  increased — it  being 
necessary  to  keep  the  vibratory  bells  at  eacli  station  in  cir- 
euits,  in  order  that  calls  may  be  heard.  By  the  use  of  con- 
densers, consisting  of  alternate  sheets  of  tin  foil  and  paraffined 
yiaper  jilaeed  around  tlic  bell  coils,  we  are  enabled  to  overcome 
the    difficulty   these  currents  would    otherwise   present.     Con- 


24 


THK   SPKAKING   TELEPHONE. 


dcnsers,  therefore,  hccoino  ahnosL  indispensable  in  cases  where 
many  telephones  are  employed  iu  one  circuit. 

The  instrument  we  have  just  described  is  made  separate  by 
itself,  to  be  used  as  a  transmitting  or  receiving  instrument,  or  it 
is  combined  in  a  box  represented  below,  with  a  call  bell  and  the 
oval  shaped  telephone  to  be  consii^ered  presently.  In  the  latter 
case  it  is  usually  employed  to  transmit  alone,  while  the  oval  form 
serves  for  receiving  ;  it  can,  however,  be  used  for  either  purpose. 


Fiij.  n. 

Mr.  Phelps  also  found  that  the  cllicieucy  of  tlic  telephone  for 
transmitting  tlio  human  voice  was  iimeh  improviMl  by  reducing 
the  cavity  or  chamber  in  which  the  diaphragm  vibrates  to  tlie 
smallest  practicable  dimensions.  Further  gain  was  also  made  by 
cushioning  the  bearings  of  the  diaphragm  on  both  sides  with 
rings  of  paper.  In  the  for;n  described  below  t!ie  diaphragms  are 
still  further   cushiuned  on  the  .side  towards  the  mauinets  by  a 


O.Xtl 

repi 
ofh 
nee 

<'011 


I'UKLPS'S   DLTLEX   TKLKPHONK. 


25 


es  where 

)arjite  by 
jnt,  or  it 
I  and  tbe 
the  latter 
3val  form 
•  purpose. 


cphouo  for 
)y  reducing 
ates  to  the 
.rio  made  by 

sides  with 
Hiragms  are 
iguets  by  a 


number  of  small  spiral  springs,  j)laced  under  a  hard  rubber  ring 
wliich  supports  the  diapliragm. 

The  value  of  these  last  named  improvements  lies  not  so  much 
in  increasing  tlie  loudness  of  tone  as  in  eliminating  the  reverber- 
atory  quality  characteristic  of  most  of  tlie  early  telephones,  and 
which  gave  an  unnatural  and  hollow  sound  to  the  voice  trans- 
mitted by  them. 


Foj.  12. 
Another  of  the  forms  designed  by  Mr.  Plielps,  and  now  being 
extensively  introduced  by  the  American  Teloiihone  Company,  is 
repn;sentc"d  in  lig.  10.  It  consi.sts  of  a  polislied  oval  shaped  case 
of  llard  rubber,  with  magnet,  diaphragm  and  coils  inside.  In  con- 
nection witli  this  there  is  also  a  small  magneto-electrical  maclime, 
toutained  in  the  oblong  box  shown  iu  fig.  11,  which  is  used  for 


26 


THE  SPEAKING  TELEPHONE. 


operating  a  call  bell  when  the  attention  of  the  correspondent 
at  the  distant  station  is  required.  The  currents  generated  by 
this  machine,  when  the  crank  is  turned,  are  convoyed  by  the 
conducting  wires  through  the  helices  of  a  [)o]arized  magnet, 
shown  on  the  under  side  of  tlie  cover,  fig.  12,  and  cause  the  ham- 
mer attached  to  the  armature  lever  to  vibrate  against  the  bell, 
thus  producing  a  violent  ringing  during  the  time  the  crank  is 
turned. 

By  the  use  of  polarized  magnets — the  latter  so  named  on 
account  of  their  armatures  being  permanent  magnets — the  arma- 
ture levers  are  retained  in  a  definite  position,  depending  upon  the 
direction  of  the  current  last  sent  into  the  line,  and  no  retractile 
spring  whatever  is  required.  At  the  same  time,  also,  the  alter- 
nating currents  produced  by  the  magneto-electrical  machine  arc 
permitted  to  act  with  their  maximum  power,  as  the  repelling 
force  exercised  in  one  pair  of  c  )ils  urges  the  armature  in  the 
same  direction  as  that  of  the  attractive  force  in  the  other,  and 
the  two  effects  are  thus  added. 

It  is  usual  to  supply  two  telephones  with  tliis  apparatus — two 
being  preferable  to  one — as  then  one  can  be  held  to  the  ear  while 
the  other  ia  being  used  to  speak  into.  By  this  means  any 
liability  of  losing  a  word  while  the  instrument  is  l)cing  passed 
from  the  month  to  the  ear,  supposing  one  <^nly  to  be  used,  is 
entirely  prevented,  and  consequently  the  necessity  for  repetition 
avoided. 

When  the  telephone  is  not  in  use  it  is  placed  in  a  slide,  as 
shown  in  fig.  11,  which  causes  a  spring,  shown  at  the  end  of  the 
box  in  fig.  12,  to  be  pressed  inward  and  cut  out  the  instrument, 
leaving  only  the  magneto  machine  and  call  bell  in  cu'ciit.  The 
spring,  when  \a  its  normal  position,  on  the  other  hand,  cuts  out 
tlie  machine  and  call  bell  and  leaves  the  telephone  alone  in 
circuit. 

Fig.  13  represents  a  somewhat  more  expensive  but  at  the  same 
time  also  a  more  desirable  combination  of  the  teleplione  and 
its  accessories.  The  box  is  intended  to  be  fastened  ]iermanently 
to  the  wall.     It  contains,  in  addition  to  the  extra  loud  telephone 


PHKLl'S'8  DUPLEX  TELKl'UONE. 


27 


3spondent 
crated  by 
3d  by  the 
I  magnet, 
3  the  liam- 
t  the  bell, 
!  crunk  is 

named  on 
-the  arma- 


upon 


the 


3  retractile 
',  the  alter- 
lachinc  are 
3  repelling 
turo  in  the 
other,  aqd 

ratus — two 
e  ear  while 
means  any 
iing  passed 
be  used,  is 
ir  repetition 

I  a  slide,  as 

Q  end  of  the 
instrument, 
rcuit.  The 
nd,  cuts  out 
no  alone  in 

b  at  the  same 
ieplione  and 
permanently 
ad  telephone 


with  double  diaphragms,  which  was  described  above,  a  call  bell 
and  a  magneto-electric  machine  of  improved  construction.  When 
not  in  use,  only  the  call  bell  of  this  apparatus  is  in  the  main  line 
circuit — the  magneto  machine,  unlike  that  in  the  box  just  noticed, 
being  cut  out,  so  as  to  guard  against  accidental  demagnetizaliou  of 


FKg.  13. 

the  permanent  magnet  by  lightning  discharges,  or  by  currents  from 
telegraph  lines  when  the  latter  are  crossed  or  in  contact  with  the 
telephone  line,  which  is  sometimes  liable  to  occur.  When  we 
wish  to  send  a  signal,  however,  it  is  only  necessary  to  turn  the 


28 


THE   SPEAKING  TELEPHONE. 


crank  of  tbo  magneto  machine,  shown  in  front  of  the  case,  and 
at  tbo  same  time  press  upon  the  push  button  C,  which  is  visible 
on  the  left.  The  latter  movement,  by  a  change  of  connection 
to  bo  more  fully  described  presently,  puts  the  magneto  machine 
in  circuit,  and  thus  allows  the  currents  generated  by  it  to  pass 
into  tlie  line  and  act  upon  the  distant  call  bells. 

The  switch  near  the  top  of  the  case  serves  for  cutting  the  ap- 
paratus in  and  out  of  circuit  When  it  is  turned  to  the  right, 
and  tho  telephone  is  in  the  fork  or  holder,  as  represented  in 
the  figure — in  which  case  it  presses  against  a  button  correspond- 
ing to  the  spring  in  the  former  box  and  cuts  itself  out  of  circuit — 
only  the  call  bell  is  left  in  with  the  main  line.     When  it  is 


Fig.  14. 

turned  to  the  loft  hand  or  opposite  side,  which  should  always  be 
done  whci  left  at  night,  all  of  the  apparatus  is  cut  out  of  circuit. 
A  lightning  arrester  is  provided  in  each  box  for  the  protection 
of  the  apparatus;  but  during  thunder  storms,  and  especially 
severe  ones,  it  is  best  to  cut  the  apparatus  out  of  circuit  altogether 
by  means  of  the  switch,  as  the  best  arresters  sometimes  fail.  The 
accompanying  diagrams,  showing  the  internal  arrangements  of 
the  different  boxes,  will  give  a  much  clearer  understanding  of 
the  connections.  Figure  14  represents  the  parts  and  connections 
of  the  improved  apparatus,  which  is  ])laced  in  a  portable  box, 
like  the  one  shown  in  ligure  11,  without,  however,  the  addition 


MAGNETO- KLB:CTKIC   JIKLI,   CAM- 


29 


of  what  wo  havo  called  tho  extra  loud  Speaking  'relcphono.  In 
tlio  ordinary  working  condition  of  tho  apparatus  the  switch  S 
should  bo  2>lac('d  on  tho  button  contact,  sliown  jimt  to  the  rigiit 
of  it,  and  the  telephone  hung  in  its  fork,  wliieh  causes  the 
spring  A  to  be  forced  against  the  insido  contact  point.  Tho 
telcplionc  and  magneto  machine  are  thus  cut  out  of  circuit, 
as  will  be  see  >  on  tK.cing  tho  connections,  but  tho  call  currents 
arriving  frc  m  a  distant  station  on  the  line,  find  a  ready  path 


TS 


Fig.  15. 
through  the  coils  of  the  bell  magnet  B  and  spring  below  the 
push  button  C  to  the  spring  A,  and  thence  by  switch  S  to  line 
again  or  ground,  as  the  case  may  be,  the  final  connection  de- 
pending, of  course,  upon  whether  the  station  is  located  some- 
where in  the  centre  or  at  the  terminal  of  the  line.  A  call  given 
liy  any  one  of  the  stations  in  the  circuits  will,  therefore,  be  heard 
at  all  tiie  others,  as  the  connections  at  each  arc  precisely  similar. 
In  giving  the  call,  it  is  necessary,  in  addition  to  turning  the 
crank  of  the  magneto  machine,  to  press  against  the  push  button 


30 


THK   SPEAKING   TELEPHONK. 


C,  SO  as  to  bring  tlie  adjacent  spring  in  contact  with  the  little 
connecting  piece  which  is  metallically  joined  to  tlie  coils  of  the 
machine.  Unless  this  is  done  no  current  will  be  sent  into  the 
line,  because  it  is  by  this  means  alone  that  the  inductive  appa- 
ratus is  placed  in  the  circuit.  When  the  button  is  down,  the 
path  opened  for  tlie  current  may  be  traced  from  the  line  terminal 
of  the  instrument  by  way  of  the  bell  and  magneto  coils  to  the 
spring  beneath  C  ;  thence  by  way  of  spring  A  and  switch  S  to 
line  or  ground. 


LIAIE 


UNE 


Fig.  IG. 

It  will  be  obvious  that  the  above  arrangement  supplies  the 
means  for  giving  a  variety  of  calls  in  case  there  are  several 
offices  in  one  circuit ;  for,  while  turning  the  crank,  the  push 
button  can  be  used,  like  a  Morse  key,  to  give  different  signals. 

The  removal  of  the  telephone  from  its  fork  or  holder  puts  it 
in  circuit,  and  cuts  everything  else  out,  as  will  readily  be  seen  by 
tracing  the  connections.  The  manner  in  which  the  apparatus  is 
cut  out  of  circuit,  by  turning  the  switch  S  on  the  lefl  hand  con- 
tact point,  will  also  be  seen  on  referring  to  the  diagram. 

Figures  15  and  16  show  the  internal  connections  and  arrange- 


(IRAYS   BATTKHV   TKLEPUOXE. 


31 


meiit  of  tlio  large  box,  figure  15,  being  the  arrangement  for  a  ter- 
minal, and  figure  16  that  for  an  intermediate  station.  The  loud 
speaking  instrument  is  shown  in  both.  Figure  16  also  shows 
the  manner  of  connecting  the  condenser  D  around  the  bell  coils, 
so  as  to  avoid  the  previously  noticed  inductive  difficulties  which 
present  themselves  when  many  sets  of  the  apj^aratus  are  placed 
in  one  circuit.  The  liglitning  arrester  is  represented  at  L.  It 
will  hardly  be  necessary  to  say  anytliing  further  in  regard  to  the 
connections  in  the  last  two  figures,  as  the  same  letters  that  were 
used  in  the  preceding  figure  have  been  retained  for  correspond- 
ing parts  in  these,  and  have,  therefore,  been  already  considered. 


Fi'J.  ' '. 

Figure  17  represents  a  form  of  Gray's  Sneaking  Telephone 
manufactured  by  the  Western  Electric  Telegraph  Company,  of 
Chicago. 

Figure  18  shows  a  section  of  the  same,  reduced  to  about  one 
third  the  natural  size,  and  designed  to  show  the  internal  mechan- 
ism. 

By  referring  to  the  latter  it  will  be  seen  that  the  core  C  is  fas- 
tened to  the  upper  end  of  the  curved  metallic  bar  II,  which 
serves  as  the  handle  of  the  telephone.  The  lower  end  of  the 
handle  is  in  like  manner  attached  to  the  metallic  brace  B.  To 
this  brace  is  secured,  by  means  of  a  stout  screw,  the  iron  rim 


32 


THE   SPEAKING  TELEPHONE. 


which  holds  the  diaphragm ;  thus  the  core  and  the  diaphragm 
form  the  two  ends  of  a  rigid  metallic  system,  every  part  of  which 
is  of  sofl  iron. 

Around  the  core  two  helices  of  insulated  copper  wire  are 
wound.  One  of  these — the  polarizing  helix — is  somewhat  longer 
than  the  other,  and  cotitains  wire  of  larger  gauge.  In  using  the 
telephone,  this  helix  is  connected  in  circuit  with  a  local  battery. 
The  soft  iron  system  is  in  consequence  rendered  magnetic,  the 
end  of  the  core  exhibiting  opposite  polarity  to  that  of  the  dia- 
phragm confronting  it. 

By  employing  the  battery  current  to  charge  the  soft  iron  core, 


Pig.  18. 

a  greater  degree  of  magnetism  is  thereby  secured  than  could  be 
obtained  by  the  use  of  a  permanent  magnet  of  the  same  dimen- 
.ons. 

The  difference  also  of  magnetic  potential  existing  between  the 
diaphragm  and  tlie  core  is  increased  by  making  these  respectively 
the  opposite  poles  of  the  same  magnet. 

The  other  hel'x  is  made  of  very  fine  wire,  and  serves  to  con- 
vey to  the  line  the  undulating  currents  induced  by  the  vibrating 
diaphragm.  At  any  point  on  the  line  these  currents  may  be 
reconverted  into  sound  by  introducing  an  instrument  similar  to 
the  above. 


GRAYS   SPEAKING  TELEPHONE. 


88 


In  adjusting  this  telephone  advantage  is  taken  of  the  elasticity 
of  the  brace  B,  which  hus  a  tendency  to  approach  the  handle 
II.  This  tendency  is  checked  and  regulated  by  the  adjusting 
.screw  A,  a  turn  of  which  will  cause  the  brace  to  move  towards 
or  recede  from  the  handle  ;  and,  consequently,  the  diaphragm  will 
also  move  to  or  recede  from  tlie  core  of  the  magnet.  • 

Another  of  the  forms  devised  by  Mr.  Gray  is  shown  in  fig.  19. 
In  I'li.  t!i(  'ire  two  diuplirapms,  and  no  battery  is  used  to 
cliarLa  iron  cores  of  the  telcplione,  tis  is  done  in  the 

original  ;qij)aratus,  the  same  result  being  obtained  by  the  use  of 
a  ]»ermanent  magnet,  bent  into  a  form  like  the  letter  U,  as  seen 
iu  the  iigiu'c.       The  niagnet  also  answers  as  a  handle,  by  which 


rves  to  con- 


Fig.  19. 

I  tlie  instrument  maybe  he. !  -on veniently.     Two  soft  iron  pieces 
I  lire  seeured  l)y  screws  to  the  poles  of  the  magnet  and  carry  helii-es 
(it  eopper  wire,  whieh  are  joined   together,  and   terminal  wires 
leading  therefrom  .serve  to  put  the  instrument  in  eireuit. 

The  mouthpiece,  wliich  is  of  metal,  lias  two  divergent  tubes  oon- 

iiivting  with  narrow  chambers,  within  whieh  .'<ej\arate  diaphragms 

I   tiiin  sheet  inm  are   ])laee(l,  so  as  to  stand  just  opjjosite  the 

"  >'(•  pieces  of  the  m.^gnet  and  in  close  proximity  thereto.     When- 

er.  therefore,  aiw    -novement  is  produceil  in  the  air  at  the 

Ji  |.(iiiiiir  of  the  till  "    're  resultant  impulse  is  readily  conveyed 

iiiiiifh  it  iind  its  l)i,ir.L'i)es  to  the  ehamiiers.  und  thus  eommuni- 

•'■s  luutiuu  to  the  diaphragms.     The  priuciple  of  the  action  in 


34 


THE   SPEAKING    TELEPHONE. 


this  apparatus  is,  of  course,  the  same  as  that  in  the  other  forms 
of  ni'iguetc)  telephones. 

It  will  be  observed  that  all  the  Speaking  Telephones  which 
we  have  described,  possess  certain  common  characteristics  em- 
bodied in  Mr.  Grav's  o;  'wi^]  discovery,  and  are  essentially  the 
same  in  principle  althougi  ing  somewhat  in  matters  of  de- 

tail. All,  for  example,  enij. .  a  diaphragm  at  the  transmitting 
end  capable  of  responding  to  the  acoustic  vibrations  of  the  air ; 
all  em])loy  a  diaphragm  at  the  receiving  end  capable  of  being 
thrown  into  vibrations  by  the  action  of  the  magnetizing  helix, 
correspondmg  to  the  vibrations  of  the  transmitting  diaphragm  ; 
all  depend  for  their  action  upon  undulating  electric  currents  pro- 
duced by  tlie  vibratory  motion  of  a  transmitting  diaphragm, 
which  increases  and  decreases  the  number  and  amplitude  of 
the  electric  impulses  transmitted  over  the  wire  without  breaking 
the  circuit;  and,  fuially,  in  all  practically  operative  tele])hones. 
whether  A'ocal  or  harmonic,  the  cores  of  the  receiving  instru- 
ment are  maintained  in  a  permanently  magnetic  state  by  the 
inductive  action,  cither  of  a  permanent  voltaic  current  or  of  a 
])ermanent  magnet.  Repeated  experiments  have  shown,  also, 
that  this  pcnnanent  magnetic  condition  of  the  cores  is  absolutely 
essential,  in  order  that  the  receiving  magnet  may  become  prop- 
erly responsive  to  telephonic  vibrations,  es])ccially  when  these 
are  of  great  rapidity  and  comparatively  small  am))litude. 

Mr.  Thomas  A.  Edison,  of  Menlo  Park,  New  Jersey,  has  in- 
vented a  telephone,  which,  like  that  of  Gray,  shown  in  figure 
6,  is  based  upon  the  principle  of  varying  the  strength  of  a  bat- 
tery current  in  unison  with  the  rise  and  fall  of  the  vocal  utter- 
ance. The  problem  of  practically  varying  the  resistance  con- 
trolled by  the  diaphragm,  so  as  to  accomplish  this  result,  was  by 
no  means  an  easy  one.  By  constant  experimenting,  however, 
Mr.  Edison  at  length  made  the  discovery  that,  when  properly 
prepared,  carbon  possessed  the  remarkable  property  of  changing 
its  resistance  with  pressure,  and  that  the  ratios  of  these  changes  j 
moreover  corresponded  exactly  with  the  pressure.  Fig.  20  rep- 
resents a  couveuicut  and  ready  way  of  showing  the  decrease  in  j 


KD13UX3   SPEAKING  TELEPHONE. 


86 


i-t'si>tancc  of  tliis  substance  when  so  sul)jeete(l.  The  dcviec^  con- 
sists (jf  ii  carhon  disk,  two  or  three  cells  of  liattery,  and  a  tan- 
'jcnl  or  other  form  of  galvanometer.  The  carl)on  C  is  ]ilaced  be- 
1  ween  two  metallic  plates  whicli  arc  jcnned  witli  the  galvanome- 
tiT  and  hatterv  in  one  circuit,  through  which  the  battery  current 
is  made  to  pass.  AVheu  a  given  weight  is  ])laced  U])on  the  u])per 
]il;ite  the  carbon  is  subjected  to  a  definit(>  amount  of  pressure, 
which  is  shown  by  the  deflection  of  tlie  galvanometer  needle 
tlinmgh  a  certain  nundier  of  degrees.  As  additional  weiglit  is 
added,  the  deflection  increases  more  and  more,  .so  that  by  care- 
fnllv  noting  tlie  deflections  corresjionding  to  the  grafbial  in- 
crease of  pressure  we  can  thus  follow  the  various  changes  of 
resistance  at   our  leisure.     Here,   then,   was  tlic  solution  ;  for, 


Fi(j.  'JO. 


by  vibrating  a  diaphragm  with  varying  degrees  of  pressure 
against  a  disk  of  carbon,  which  is  made  to  form  a  portion 
of  an  electric  circuit,  the  resistance  of  the  disk  would  vary  iu 
])reci.se  accordance  with  the  degreaof  pressure,  and  consequently 
a  proportionate  variicion  would  be  occasioned  in  the  strength  of 
the  current.  The  latter  would  thas  possess  all  the  character- 
istics of  the  vocal  waves,  and  by  its  reaction  through  the  medium 
of  an  electro-magnet,  might  then  transfer  them  to  another  disk, 
causing  the  latter  to  vibrate,  and  thus  reproduce  audible  speech. 
Fig.  21  shows  the  telephone  as  constructed  1)y  Mr.  Edi- 
son. The  carbon  disk  is  represented  by  the  black  portion,  E, 
near  the  diaphragm,  A  A,  placed  between  two  platinum  plates, 
I '  and  G,  which  arc  connected  in  the  battery  circuit,  as  shown  by 
till'  lines.  A  small  piece  of  rubber  tubing,  B,  is  attached  to  the 
('••ntreof  the  metallic  diaphragm,  and  presses  lightly  against  an 
ivory  piece,  C,  which  is  placed  directly  over  one  of  the  platinum 


36 


THE   SPEAKING  TELEPUONE. 


plates.  Whenever,  therefore,  any  motion  is  given  to  the  dia- 
phragm, it  is  immediately  followed  by  a  corresponding  pressure 
upon  the  carbon  and  by  a  change  of  resistance  in  the  latter,  as 
described  above.  The  object  in  using  the  rubber  ju.^t  mentioned 
is  to  dampen  the  movement  of  the  di.^k,  so  as  to  l)ringit  to  rest 
almost  immediately  after  the  cau.se  which  juit  it  in  motion  has 
ceased  to  act ;  interference  with  articulation,  which  the  prolonged 
vibration  of  the  metal  tends  to  produce  in  consequence  of  its 


Fig.  21. 

elasticity,  is  thus  prevented,  and  the  sound  comes  out  clear 
and  distinct  It  is  obvious  that  any  electro-magnet,  properly 
fitted  with  an  iron  diaphragm,  will  answer  for  a  receiving  instru- 
ment in  connection  with  this  apparatus. 

Fig.  22  shows  a  sending  and  receiving  telephone  and  a  box 
containing  the  battery. 

In  the  latest  form  of  transmitter  which  Mr.  Edison  has  intro- 
duced the  vibrating  diaphragm  is  done  away  witli  altogether,  it 
having  been  found  that  much  better  results  are  obtained  when  a 


EDISON'S  SPEAKING  TELEPHONE. 


37 


.ison  lias  intro- 
Iv  altogether,  it 
,btained  when  a. 


rigid  plate  of  metal  is  substituted  in  its  place.  With  the  old 
vibrating  diaphnigni  the  articulation  produced  in  the  receiver  is 
more  or  less  muffled,  owing  to  slight  changes  which  the  vibrating 
disk  ocea.sioiis  in  tlie  pre^ssure,  and  which  probably  results  from 
tanly  dampening  of  the  vibrations  after  having  been  once 
started.    In  the  new  arrangement,  however,  the  articulatioa  is 


Fig.  22. 

SO  clear  and  exceedingly  well  rendered  that  a  whi.sper  even  may 
readily  be  transmitted  and  understood.  The  inllexible  plate,  of 
c'oni'se,  merely  serves,  in  consequence  of  its  comparatively  large 
area,  to  concentrate  a  considerable  portion  of  the  sonorous  waves 
11]  lull  tlie  small  carbon  disk  or  button ;  a  much  greater  degree  of 
pressure  for  any  given  elTort  on  the  i)art  of  the  speaker  is  thus 


88 


THE   SPEAKIXG   TELEPHONE. 


lironght  to  boar  on  the  disk  thuu  could  l>o  ubtaiuod  if  only  its 
small  surface  ulono  were  used. 

The  best  substance  so  far  discovered  for  these  disks  is  lamp- 
black, such  as  is  produced  by  the  burnnig  of  any  of  the  lighter 
hydrocarbons.  Mr.  Edison  has  found,  however,  that  plumbago, 
hy])eroxidc  of  lead,  iodide  of  copper,  powdered  gas  ret(jrt  car- 
bon, Uack  oxide  of  manganese,  amor])hous  phosphorus,  ihiely  di- 
vided metals,  and  inan\'  sulphides  may  be  u.sed ;  indeed,  tufts  of 
fibre,  coated  with  various  metals  by  chemical  means  and  pres.sed 
into  buttons  have  also  been  eni[)loyed,  but  tliey  are  all  less  sensi- 
tive than  the  lampblack,  and  have  consequently  been  abandoned 
for  the  latter  substance. 

With  the  telephone,  as  with  the  ordinary  telegi-aphic  instru- 
ments, there  is  of  course  a  limit  beyond  which  the  apparatus  cannot 
be  rendered  practically  serviceable,  but  in  most  cases  this  limit  is 
sooner  reached  for  the  telephone  than  for  other  instruments  that 
are  employed  for  the  transmission  of  telegraphic  matter.  One 
reason  why  this  is  so  is  ])robably  due  to  the  fact  that  the  ciuTcnt 
pulsations  generated  by  the  vibrating  diaplu-agm  arc  made  to 
follow  each  other  with  so  much  greater  rapidity  than  those  that 
are  sent  into  the  line  by  the  ordinary  hand  manipulation,  that 
less  time  is  allowed  for  charging  and  discharging  the  line,  and 
the  phenomenon  of  inductive  retardation  thus  becomes  soonest 
manifest  in  the  former  case. 

Another  reason,  however,  and  perhaps  the  principal  one,  is 
that  the  disturbances  created  by  the  inductive  action  of  elec- 
trical currents  in  neighboring  wires  combine  with  the  signals,  and 
so  confuse  the  latter  in  many  cases,  that  it  becomes  altogether 
impossible  to  distinguish  them.  It  is  necessary,  tlierefore,  when 
we  wish  to  speak  over  long  di.stance.«.  or  over  wires  in  close  prox- 
imity to  Morse  lines,  either  to  employ  some  nicans  for  neutral- 
izing these  disturbances,  or  to  so  increase  the  loudness  of  the  ar- 
ticulation that  it  can  be  heard  above  this  confused  mingling  of 
many  sounds. 

One  of  the  best  means  so  far  suggested  for  overcoming  the  diffi- 
culty is  the  employment  of  metallic  circuits  throughout  for  the 


EDISOXS   TELEPIIOXTC   REPEATER. 


39 


trlqilinnc,  placiiif?  the  two  wires  forming  a  single  circuit  very 
(•los(!  together,  so  as  to  render  tlio  iuductivo  netion  ])racticaily 
tlie  same  in  eacli.  Tlie  resulting  currents  would  thus  neutralize 
each  other  and  leave  the  telephone  rpiite  free. 

It  is  claimed  that  the  inductiv^c  disturbances  just  noticed  are 
much  less  marked  witli  Mr.  Edison's  tele])hone  than  with  any 
of  the  other  forms,  owing  to  the  fact  that  the  signals  or  sounds 
in  the  former  are  produced  by  stronger  currents,  and  the  re- 
eeiving  iTistrumcnts  arc  made  less  sensitive  to  those  fugitive 
currents  that  are  always  met  with  in  telegraph  lines. 

!^^r.  Edison  has  recently  invented  a  telephonic  repeater,  which 
is  designed  to  bo  used  in  connection  Vi'ith  his  a})2)aratus  for  in- 
creasing the  distance  over  which  it  may  be  made  available.  The 
principal  ]iarts  are  shown  in  fig.  23.  I  is  an  inductioQ  coil,  whose 


M 


^t-. 


i 


Fi'j.  2.3. 


pocondary  is  connected  in  the  main  line  L',  into  which  the  repeat- 
ing is  to  be  done;  C  is  a  carbon  transmitter,  included  with 
hattery  B  in  the  primary  circuit,  and  op(>rated  by  the  magnet 
M  instead  of  by  the  voice.  The  variations  in  the  current  pro- 
duced by  speaking  against  the  disk  of  the  instrument  at  the 
transmitting  end  of  the  line,  cause  this  magnet  to  act  on  the  re- 
lieater  diaphragm,  and  thus  jiroduce  different  degrees  of  pressure 
im  the  carbon  disk  and  thereby  change  its  resistance.  A  coitg- 
sponding  cliange  consef|uently  takes  ]»lae(!  in  the  current  of  the 
lirimary  coil,  and  thus  gives  rise  to  a  series  of  induce. 1  currents 
in  the   secondary,  which  i)ass  into  the  line,  and,  on  reaching 


40 


THE   SPEAKING   TELEPHONE. 


the  receiver  at  the  opposite  terminal,  are  there  transformed  into 
uu(li1)le  sound. 

Wc  have  not  yet  personally  experimented  with  this  apparatus, 
but  if  it  can  be  made  only  in  a  .'flight  degree  as  elfectivo  as  the 
ordinary  carljon  telephones,  which  already  have  2:)ermitted  conver- 
sation to  be  carried  on  over  five  hundred  miles  of  actual  tele- 
grai)h  line,  its  advantage  must  sooner  or  later  l)c  made  ser- 
viceable.   ' 

Instead  of  tlie  magneto  machine  and  call  bell,  which  have 
already  been  described  in  connection  with  the  telephone,  a  bat- 


tery and  vibrating  bell  may  be,  and  sometimes  arc  used  for  sig- 
naling purposes.  Fig.  24  represents  the  connections  for  an 
arrangement  of  this  kind.  The  line  wire  is  joined  to  the  back 
end  of  a  four  point  button  switch,  S.  The  right  hand  front  con- 
tact leads  to  one  end  of  the  helices  which  surround  the  bell 
magnet,  and  whose  opposite  end  is  in  metallic  connection  with 
the  armature  lever.  In  its  normal  ])ositi(in  this  lever  is  held  by 
a  spiral  spring  against  the  back  stop,  which  is  joined  to  a  wire 
leading  to  the  ground.  The  middle  front  point  ot  the  switch 
communicates  with  one  pole  of  a  battery.  E.  whose  opposite  ])oie 


TELEPIIOXK   AXn  VIBBATINTr   HEI,I,. 


41 


is  ill  connection  with  tlio  ground  wire,  and  tlio  left  hand  point  is 
coiiiu'ctc'd  to  one  or  two  telephones,  T,  iilso  in  coinmunieation 
willi  tli(!  ground. 

Wlicii  the  iipparatus  is  not  being  used  the  switch  is  hh  on 
llic  riglit  hand  contact,  so  that  a  cun-cnt  coming  from  tiie  line 
liiis  a  frt'o  })atli  through  the  lieliccs,  armature  lever  and  hack 
stop  to  cartli.  Tlie  soft  iron  core  is  thus  rendered  magnetic  and 
attracts  tlie  anuaturc,  Init  after  the  latter  has  moved  ii  short 
distance  it  leaves  the  sjmng  forming  \nirt  of  the  back  stop,  and 
in  so  doing  lireaka  the  circuit  The  magnetism  of  the  cores 
coiiscMpieiitly  disajijiears,  and  the  armature  is  drawn  back  so  as 
to  complete  the  circuit  once  more,  when  another  attraction  fol- 
lows, and  so  the  jirocess  goes  on  alternating  as  long  as  battery 
is  i<ej)t  on  at  the  distant  station.  Kach  attraction,  tlicrefore, 
occasions  a  distinct  tap  upon  the  bell,  and  as  tlu;  magnetization 
and  demagnetization  are  exceedingly  rapid,  the  taps  consetpuMitly 
su('ccc(l  each  other  with  sullicient  rapidity  to  keep  up  a  continu- 
ous riii'nn<r. 

If  the  attendant  at  the  distant  station  is  wanted,  tlie  switch  is 
])laccd  on  the  middle  contact,  which  allows  the  ('urrcnt  from  bat- 
tery K  to  jiass  into  the  line,  causing  the  distant  bell  to  ring.  Tlie 
switch  is  then  turned  to  the  right  again,  when,  if  tlie  .signal  lias 
been  observed,  an  acknowledgment  to  that  elfcct  is  given  by  the 
<listant  corrc.^^jiondcnt  placing  his  battery  in  circuit,  and  thereby 
in  turn  causing  tlie  bell  at  the  .station  which  originally  gave  the 
.-signal  to  ring.  Both  .switches  are  then  turned  to  the  left  hand 
side,  l)y  which  means  the  tcleiihoncs  are  jmt  in  circuit  and  made 
availal)le  for  the  interchange  oi  correspondence. 

Fig.  25  shows  an  aiTangement  for  a  ^lorse  and  telephone  com- 
bination, which  in  many  cases  it  is  very  convenient  to  have. 
When  the  switch  is  turned  onto  the  right  hand  contact  point 
the  Monse  apparatus  is  in  circuit,  and  can  tlien  be  used  for  the 
exchange  of  business  in  the  ordinary  wa\-.  The  Morse  apjiaratus 
answers  also  for  a  call  to  attract  the  attention  of  a  corr(>spoiident 
when  wanted  ;  the  local  battery  has  been  oiuitted  in  the  diagram. 
"When  the  switch  is  turned  to  the  left  the  telephones  alone  are 
in  circuit. 


42 


TlIK   Sl'KAKINO  TELEI'irONK. 


Ik'foro  Ic'iviiit^'  \\n'  snlijcH't  we  iimst  iikhv  partionlarlv  mention 
()'  e  imiiit  ill  cnniu'ctiiiii  therewith  that,  is  of  ton  niueh  interest  to 
lie  ()vei'h)()keil.  Tiiis  is  in  ivhitioii  to  the  various  charaeteristicM 
or  forms  of  action  that  taive  j)hiei!  in  the  transmission  of  articu- 
late speech,  and  which  furnish  ns,  in  the  o|)eration  of  tlio 
Spoiiking  'J'cle|)lioiie,  with  a  most  beautiful  illustration  of  the 
correlation  of  forces,  or  of  their  mutual  convcrtibilit}'  from 
one  form  into  another.  When  wc  speak  into  a  tclcpliono 
the  muscular  elforts  exerted  npon  the  luugs  force  the  air 
through  the  larynx,  within  which  are  situated  two  mcm])ranc3 
called  the  vocal  chords.     Tiiose  can  be  tightened  or  relaxed  at 


will  by  the  use  of  certain  muscles,  and,  being  thrown  into  vibra- 
tion by  the  passage  of  the  air,  give  rise  to  a  series  of  sonorous 
waves  or  aerial  pulsations,  varying  in  pitch  witli  the  tension  or 
laxity  of  the  chords.  The  impact  of  there  pulsations  against  the 
metallic  diaphragm  produces,  in  turn,  corresponding  vibrations 
of  the  latter,  wliich,  as  we  have  seen,  is  in  close  proximity  to  the 
poles  of  a  permanent  magnet.  By  tliis  means,  therefore,  the 
inductive  action  of  the  diaphragm  on  tlie  magnet  is  called  into 
play,  and  there  is  consequently  generated  in  the  surrounding 
helix  a  series  of  electrical  currents,  which  the  intervening  con- 


CORUELATIO.V  oi'   KOUCE3. 


43 


ductor  conveys  to  tlio  distant  station,  wliero  their  further  action 
is  then  spent  in  the  j)roductioii  of  magnetism.  Tho  receiving 
diaphragm,  being  then  thrown  into  vihralion  by  tlic  resalting 
attractions,  rcsjioiid.s  with  faithful  accuracy  to  tho  vibrations 
origiudly  produced  at  tho  transmitting  end  of  the  line,  and  thus 


Pi-J.  20. 

also  reproduces  those  sonorous  waves  which  reach  the  ear  and 
give  us  the  sensation  of  sound.  Here,  then,  we  have,  first,  the 
mechanical  cfFects  of  muscular  action  converted  into  electricity, 
then  into  magnetism,  and  finally  back  again  into  mechanical 
action.      At   each   transformation,  however,  a  portion  of  the 


u 


THK   Sl'EAKlxa   TELEPHONE. 


energy  is  lost,  so  far  us  its  available  usefulness  is  concerned  ;  and, 
therefore,  the  sound  waves  which  reach  the  car,  althougli  pre- 
cisely similar  in  pitch  and  quality  to  those  first  produced  by  the 
vocal  organs,  are  nevertheless  much  enfeebled — their  amplitude, 
on  which  alone  loudness  depends,  being  diminished  by  the 
amount  of  energy  lost  in  the  transformation. 


rOj.  27. 

During  tlie  past  year  the  articulating  or  Speaking  Telephone 
has  attracted  very  general  interest  and  attention,  not  only  in  this 
country  but  also  in  Euroj)e.  It  has  already  been  extensi\-fly 
introduced  here  upon  inany  of  cur  .'<hort  lines,  and  bids  fair  d. 
become  of  almost  universal  application  in  a  very  sliort  time,  its 


P(jri:LAKITV    OF    TICK    TKI.KI'IIOXK. 


45 


extreme  simplicity  iuid  tlio  rcliuhility  of  its  (jperatiou  rendering 
it  (ino  of  the  most  convenient  of  the  many  electrical  appliances 
in  use.  In  Germany  it  has  been  adopted  as  a  part  ot  the  tele- 
gi'aph  system  of  the  country,  and  there,  as  well  as  in  other  foreign 
countries,  it  is  also  being  generally  introduced  for  various  private 
])urposes,  for  establishing  communication  with  tlie  interior  of  coal 


iVj/.  28. 

and  iron  mines,  and  for  facilitating  the  carrying  on  of  a  multitude 
of  industries  of  various  kinds. 

The  intmmoralile  uses  to  which  the  tclc])honc  has  already  been 
applied  shows  more  forcibly  than  anything  else  its  practical  im- 
portance, and    the    advantages    it   allords   for   communicating 


4(3 


THE   SPEAKING  TELErilONE. 


between  places  separated  even  by  comparatively  long  distances  ; 
no  more  convenient  or  serviceable  instrument  for  this  jiurpose 
has  ever  been  ])rodnced,  while  at  the  same  time  it  is  capable  of 
being  used  by  every  one.  It  can  also  be  united  with  the  District 
Telegraph  system,  so  extensively  developed  here,  and  thereby 
the  range  of  the  latter  system,  wliich  is  now  limited  to  a  few 
special  calls,  such  as  police,  fire,  hack,  etc.,  may  be  very  much 
extended  and  imi)roved.  In  addition  to  this  again,  its  connection 
with  the  general  telegraph  system  will  soon  greatly  increase  the 
usefulness  of  that  service,  bv  bringing  many  villages  and  hamlets 
that  are  now  destitute  of  any  telegraphic  facilities  whatever  into 
communication  with  the  rest  of  the  world.  Hitherto  the  great 
ob.stacle  in  the  way  of  acconij)lishing  this  object  lias  been  the 
ex^jcnse  of  keeping  skilled  employes  at  such  jilaces,  where  the 
business  receipts  are  usually  less  than  would  be  required  to  pay 
the  salary  of  an  operator.  The  application  of  the  telephone, 
however,  now  provides  the  means  of  connecting  these  jjlaces  to 
the  nearest  telegraph  office  with  ver\^  little  trouble  and  with  little 
or  no  outlay  for  running  expenses.  Wc  may  therefore  confidentlv 
expect  that  another  year  or  two  will  r^uffice  to  establish  telegraph 
commimication  with  nearly  every  place  in  the  country. 

The  apparatus,  as  at  present  furnished  to  the  public  by  the 
American  Speaking  Tele})h(mo  Co.,  is  all  contained  in  a  neatly 
finished  oblong  box,  whicli  lias  ah'cady  been  described  on 
pages  25  and  26.     Figs.  11  and  12  show  the  outfit  complete. 

Fig.  26  gives  a  large  size  front  view  of  the  telephone,  and 
also  shows  the  manner  of  holding  it  when  in  use.  Manu- 
facturers and  others,  whose  workd  are  situated  at  some  dis- 
tance from  their  offices,  will  hardly  need  to  be  told  of  the 
advantages  that  may  be  derived  from  the  u.°e  of  the  telephone, 
whereby  they  are  at  all  times  practically  enabled  to  oversee  and 
personally  superintend  the  details  of  affairs  at  the  works  ;  these 
must  be  evident  to  every  one.  It  will  also  appear  equally 
obvious  that  large  and  expensive  warehouses  may  in  many  cases 
be  dispensed  with  in  cities  where  rents  are  always  high,  the 
telephone  rendering   it  possible  to  fill  orders  at   a   moment's 


BAILLES  TKLEPIIONK   PROPHECY. 


47 


notice  directly  from  the  factory  or  works  quite  as  readily  as  from 
the  warehouse,  and  at  much  less  expense.  Figs.  27  and  28  clearly 
illustrate  the  facility  with  which  communication  may  he  main- 
tained between  ofTice  and  factory,  and  plainly  show  to  what  ex- 
tent personal  suj^ervision  may  be  exercised  without  at  all  neces- 
sitating the  presence  of  the  managing  director  at  the  place  itself. 
In  the  former  figure  the  manager  at  his  desk  in  the  city  is  seen 
giving  instructions  to  his  foreman,  who  is  shown  at  the  works  in 
the  latter,  carefully  noting  everything  that  is  being  said. 

As  a  matter  of  projjhetic  interest  in  connection  with  the  tele- 
plione  we  feel  constrained  to  r(?produce  here  an  extract  from  a 
popular  little  work,  ])ul)lishod  a  few  years  ago  in  France.^  The 
author,  as  will  be  seen,  strikingly  foreshadows  the  realization  of 
the  Speaking  Telephone  as  it  exists  to-day,  compKitc;  in  every- 
thing but  loudness  of  articulation.  Speaking  of  the  marvels  in 
telegraphy,  he  says ; 

"Wonderful  as  are  these  achievenionts,  the  inventions  in  tole- 
gi'aphy  have  gone  still  further.  To  be  able  to  transmit  tlujuglit 
to  a  distance  is  a  triumph  which  was  fonncrly  astonishing;  but 
we  arc  now  accustomed  to  it,  and  continue  to  practice  it  without 
its  creating  the  slightest  wonder.  To  bo  able  to  transmit  hand- 
writing, and  even  drawings,  appeared  to  be  more  difficult ;  but 
this  problem  has  also  been  resolved,  and  we  now  hardly  wonder 
that  this  feat  is  accomplished  by  means  so  simple.  Mankind 
ever  requires  a  new  stimulus  to  its  curiosity,  and  already  it  is 
looking  forward  to  the  discovery  of  more  marvels  in  telegraphy. 
Some  year's  hence,  for  all  we  know,  wc  may  be  able  to  transmit 
the  vocal  message  itself,  with  the  very  inflection,  tone  and  ac- 
cent of  the  speaker.  Already  lias  the  acoustic  telegraph  been 
invented  ;  the  principle  has  been  discovered,  ami  it  only  remains 
to  render  the  invention  practicable  and  useful — a  result  which, 
in  these  days  of  science,  does  not  appear  to  bo  impossibla 

Sound,  of  whatever  kind,  is  produced  by  a  series  of  vibra- 
tions, more  or  less  rapid,  which,  setting  out  from  a  sonorous 


'  Lei  Mtrveillen  dt  t EUctrieiti ,  par  J.  JiailU.     Puria,  IsTl. 


48 


TIIK   Sl'KAKIXG  TKLKPIIOXE. 


liody,  traverse  tlie  air  aiul  reach  our  car.  Just  as  a  stone, 
dropped  into  a  i)ond,  throws  oil  a  succession  of  circular  undu- 
lations or  water  rings,  so  a  concussion,  acting  on  the  air,  pro- 
duces analogous  vibrations,  tliough  tliey  ai'o  invisible,  and  it  is 
when  these  vibrations  reach  the  car  that  we  become!  sensible  of 
sound,  llelrnholtz,  an  eminent  German  scientist,  has  analyzed 
the  human  voice  and  determined  its  musical  value.  According 
to  him  eacli  simple  vowel  is  formed  l)y  one  or  more  notes  of  the 
scale,  accompanied  l)y  other  and  feebler  notes  which  are  harmo- 
nics of  these.  He  demonstrates  that  it  is  the  union  of  all  these 
notes  that  give  quality  to  the  voice.  Every  syllable  is  formed  by 
the  notes  of  the  vowel  accomplished  bv<bffercnt  movements  of 
the  organs  of  the  mouth.  llelrnholtz,  reflecting  upon  this, 
thinks  it  would  be  jiossible  to  construct  a  human  voice  by  artifi- 
cially producing  and  combining  the  elementary  sounds  of  which 
it  is  composed.  This  is  not  the  place  to  discuss  such  theories, 
but  if  we  grant  that  there  is  any  truth  in  them,  wo  can  under- 
stand that  the  acoustic  telegraph  can  be  invented  and  can  trans- 
mit the  living  voice.  Already  experiments  have  been  made  in 
this  direction. 

A  vibrating  plate  produces  a  sound,  and,  acconliug  to  the 
rapidity  of  the  vibrations,  these  sounds  are  sharp  or  flat.  At 
each  of  the  vibrations  the  plate  touches  a  small  point  plact^<l  in 
front  of  it,  and  this  contact  suflices  to  throw  the  current  into  the 
line.  "When  the  plate  ceases  to  vibrate  and  retmiis  to  in  posi- 
tion of  equilibrium,  it  no  hmger  touches  the  metal  point  iiiid  the 
current  is  consequently  intemiptcd.  By  this  means  is  (jl)tained 
a  series  of  interraptions,  moro  or  less  ra[)id,  according  to  the 
sound,  the  current  being  thrown  into  the  line  and  interrupted 
once  for  each  of  the  vibration.s. 

At  the  extremity  of  the  line  the  current  enters  an  electro- 
magnet, whicli  attracts  another  vibrating  plate  of  size  and  qual- 
ity identical  with  the  former.  Attracted  and  repelled  very 
rapidly,  exactly,  and  as  rapidly  in  fact  as  the  plato  mentioned 
above,  this  second  plate  gives  forth  a  sound  which  will  havo  the 
same  musical  value  as  that  of  the  other,  as  the  number  of  vibra- 
tions per  second  is  the  same  in  both  cases. 


BAILLES  TELKPHOXE   PROPHECY. 


49 


111 

lUe 

)()si- 

ihc 

ued 

the 

ipted 

ctro 

very 
iouod 
-o  the 
vibra- 


Shovild  tliis  process  be  perfected  it  will  be  possible  to  transmit 
sound  by  means  of  the  telegraph — to  transmit  a  series  of  sounds, 
a  tune,  or  spoken  sentence  and  conversation.  This  consumma- 
tion has  not,  however,  been  yet  attained.  Many  experiments 
have  been  made,  the  principle  has  been  applied  in  divers  ways, 
and  everything  makes  us  hope  that  we  will  yet  arrive  at  a  perfect 
system  of  acoustic  telegraphy.  Advances  have  been  made  very 
far  upon  the  road  to  success.  A  scries  of  vibrating  plates,  an- 
swering to  the  strings  of  a  harp,  has  been  arranged,  each  of 
which  vibrates  when  struck  by  a  particular  sound,  and  sends  off 
electricity  to  create  at  the  end  of  a  line  the  same  vibrations  in  a 
corresponding  ])late,  or,  in  otlier  words,  to  reproduce  the  same 
sound. 

This  system,  it  must  ho  admitted,  is  at  least  very  ingenious. 
Experiments  have  been  made  in  laboratories,  that  is  to  say  under 
conditions  entirely  favorable,  and  such  as  wo  would  not  often 
find  in  actual  practice.  Under  tlieso  conditions  a  musical  air 
has  actually  been  successfully  transmitted  by  this  acoustic  tele- 
graph. All  must  admit  that  this  is  a  promising  beginning ;  but 
we  must  not  make  too  much  haste  to  exalt  the  miracle  and  to 
extol  the  advantages  of  the  future  machine,  or  to  abandon  our- 
selves to  the  indidgence  in  indiscriminate  laudation  on  the 
strength  of  this  new  discovery.  That  would  be  a  gross  mistake 
and  an  injury  to  science.  True  scientific  faith  is  doubt,  until 
the  truth  a})peai's  in  uncontrovertible  clearness.  Care  must  be 
taken  not  to  take  for  reality  that  which  is  merely  a  desire  on  our 
part  We  must  guard  against  all  premature  exiUtation,  because 
it  weakens  us  in  the  search  for  truth,  and  because  even  one  de- 
ception is  crueL  Let  us  therefore  give  to  doubt,  to  patience  and 
to  perseverance,  the  place  which  some  too  readily  give  U)  con- 
gratulation." 


CHArTKii  ir. 


BELLS  TKLKl'IIOXIU   KKSEAKCIIKS. 


In  a  lecture  delivered  before  the  Society  of  Telcpaapli  En- 
gineers, in  Loudon,  October  31st,  1877,  I'n^f.  A-  G.  Bell  gave  a 
history  of  his  researches  in  telej^liony,  together  with  the  experi- 
ments that  he  was  Icci  to  undertake  in  his  endeavors  to  produce 
a  practical  sjsteni  oi  inultijjle  to]egrai)liy,  and  to  reali^ie  also  the 
transmission  of  articulate  speech.  As  the  subject  has  now  be- 
come of  gi'or.t  interc.it,  both  in  a  s(;ientiiic  and  popular  point  of 
view,  we  feel  varranted  in  reproducing  the  lecture  in  full  After 
the  usual  intro:':Uction,  Professor  Bell  said : 

''  It  is  to-night  my  pleasure,  as  well  as  duty,  to  give  you  some 
account  of  tlie  telcjihonic  researches  in  which  I  have  been  so 
long  engaged.  Many  3'ears  ago  my  attention  was  directed  to 
the  mechanism  of  speech  by  my  father,  Alexander  Melville 
Bell,  of  Edinburgh,  who  lias  made  a  life-long  study  of  the 
subject.  Many  of  tliose  present  may  recollect  tlic  invention 
by  my  father  of  a  means  of  representing,  in  a  wonderfully  ac- 
curate manner,  the  2)ositions  of  the  vocal  (Mgans  in  forming 
sounds.  Together  wo  can'ied  on  quite  a  number  of  experiments, 
seeking  to  discover  the  correct  mechanism  of  English  and  foreign 
elements  of  speech,  and  I  remember  especially  an  investigation 
in  which  we  were  engaged  concerning  the  musical  relations  of 
vowel  sounds.  When  vowel  sounds  arc  whispered,  each  vowel 
seems  to  jiossess  a  particular  Y>itch.  of  its  own,  and  by  whispering 
certixin  vowels  in  succession  a  musical  scale  can  be  distinctly 
perceived.  Our  aim  was  to  determine  the  natural  pitch  of  each 
vowel ;  but  unexpected  difficulties  nuuh;  their  appearance,  for 
many  of  the  vowels  seemed  to  possess  a  double  2>iteh— one  due, 
probably,  to  the  resonance  of  the  air  in  the  }nouth,  and  the  other 
to  the  resonance  of  the  air  contained  in  the  cavity  behind  the 
tongue,  comprehending  the  j)harynx  and  larynx. 


lIKLMlIOi;i'/,  S   KXl'f^RlMKNTS. 


51 


I  liit  upoii  an  expedient  for  determining  the  jiitch,  which,  at 
tliat  time,  1  thought  to  he  original  with  inyself.  It  eonsisted  in 
\ibrating  a  tuning  fork  in  front  of  the  mouth  while  the  positions 
of  the  vocal  organs  for  tlie  various  vowel  sounds  were  silently 
taken.  It  was  found  that  each  vowel  position  caused  the  rein- 
forcement of  some  particular  fork  or  forks. 

I  wrote  an  at-count  of  these  researches  to  Mr.  Alex.  J,  Ellii?, 
( >f  London,  whom  I  liave  very  great  i)leasnre  in  seeing  here  to- 
night In  reply,  he  informed  me  that  the  experiments  related 
had  already  been  performed  hy  Ilelmholtz,  and  in  n  much  more 
perfect  manner  than  I  had  done.  Indeed,  he  said  that  Helm- 
holtz  had  not  only  analyzed  the  vowel  sounds  into  their  con- 
stituent nmsical  elements,  but  had  actually  jjerformed  the  syn- 
thesis of  them. 

lie  had  succeeded  in  jjroducing,  artillcially,  certain  of  the 
A-owel  sounds  by  causing  timing  forks  of  diJQEerent  pitch  to  vi- 
brato simultaneously  by  means  of  an  electrio  current  Mr.  Ellis 
was  kind  enough  to  grant  me  an  intervi(.'w  for  the  jjui-pose  of 
explaining  the  apparatus  employed  by  Ilelmholtz  in  2)roducing 
these  extraordinary  effects,  and  I  spent  the  greater  part  of  a  de- 
lightful (lay  with  him  in  investigating  the  subject  At  that 
time,  however,  I  was  too  slightly  acquainted  with  the  laws  of 
electricity  fully  to  understand  the  explanations  given ;  but  the 
interview  had  the  effect  of  arousing  my  interest  in  the  subjects 
of  sound  and  electricity,  and  I  did  not  rest  until  I  had  obtained 
])Osscssiou  of  a  copy  of  Ilelmholtz's  great  work,^  and  had  at- 
temi^ted,  in  a  crude  and  imperfect  manner  it  is  true,  to  reproduce 
his  results.  While  reflecting  upon  the  possibilities  of  the  pro- 
duction of  sound  by  electrical  means,  it  struck  mo  that  the  prin- 
ciple of  vibrating  a  tuning  fork  by  the  intermittent  attraction  of 
an  electro-magnet  might  be  apjolicd  to  tlio  electrical  production 
of  music 

I  imaginc(l  to  myself  a  series  of  tuning  forks  of  dilferent 
pitches,  arranged  to  vibrate  automatically  in  the  manner  shown 


1  Ilelmholtz.      Die  Lohro  von  dom  Tonompflndungon.     (Unglisli  translation,  hy 
Aleiundor  J.  Ellis,  Theory  of  Tone.) 


52 


THK   SPEAKING  TELEPHONE. 


by  Helmholtz — eacli  fork  interrupting,  at  every  vibration,  a  vol- 
taic current — and  the  thought  occurred,  Why  should  not  the 
depression  of  a  key  like  that  of  a  piano  direct  the  inteiTupted 
current  from  any  one  of  these  forks,  through  a  telegraph  wire,  to 
a  series  of  electro-magnets  operating  the  strings  of  a  piano  or 
other  musical  instrument,  in  which  case  a  person  might  plfiy  the 
tuning  fork  ])iano  in  one  place  and  the  music  be  audible  from 
the  electro-niagnetic  piano  in  a  distant  city  ? 

The  more  I  reflected  upon  this  arrangement  the  more  feasible 
did  it  seem  to  me  ;  indeed,  I  saw  no  reason  why  the  depression 
of  a  number  of  ke3-s  at  the  tuning  fork'  end  of  the  circuit  should 
not  be  followed  by  the  audible  production  of  a  full  chord  from 
the  piano  in  the  distant  city,  each  tuning  fork  affecting  at  the  re- 
ceiving end  that  string  of  the  piano  with  which  it  was  in  unison. 
At  this  time  the  interest  wliich  T  felt  in  electricity  led  me  to 
study  the  various  systems  of  telegraphy  in  use  in  this  country 
and  in  America.  I  was  much  struck  with  the  simplicity  of  the 
Morse  alphabet,  and  with  the  fact  that  it  could  be  read  by  sound. 
Instead  of  having  the  dots  and  dashes  recorded  upon  papei*,  the 
operators  were  in  the  habit  of  observing  the  duration  of  the  click 
of  the  instruments,  and  in  this  way  were  enabled  to  distinguish 
by  ear  the  various  signals. 

It  struck  me  that  in  a  similar  manner  the  duration  of  a  musi- 
cal note  might  be  made  to  represent  the  dot  or  dash  of  the  tele- 
graph code,  so  that  a  person  might  operate  one  of  the  ke3'3  of 
the  tuning  fork  piano  referred  to  above,  and  the  duration  of  the 
sound  proceeding  from  the  corresponding  string  of  the  distant 
piano  be  observed  by  an  operator  stationed  there.  It  seemed  to 
me  that  in  this  way  a  number  of  distinct  telegraph  messages 
might  be  sent  simultaneously  from  the  tuning  fork  piano  to  the 
other  end  of  the  circuit  by  operators,  each  manipulating  a  differ- 
ent key  of  the  instrument  These  messages  would  be  read  by 
operators  stationed  at  tlic  distant  piano,  each  receiving  operator 
listening  for  signals  of  a  certain  definite  pitch,  and  ignoring  all 
others.  In  this  way  could  be  accomplished  the  simultaneous 
transmission  of  a  numl>cr  of  telegraphic  messages  along  a  single 


tel 
pe( 


pii 
anr 


TELErilOXIO  CURREXTS. 


68 


a  vol- 
)t  the 
•upted 
rirc,  to 
ano  or 
lay  tlie 
e  from 

[casible 
)ression 
,  should 
rd  from 
t  the  re- 
.  tiuison. 
1  me  to 
country 
;y  of  the 
)y  sound, 
aper,  the 
the  cUck 
stinguish 

(f  a  niusi- 
the  tele- 
e  key3  of 
iou  o£  the 
ae  distant 
seemed  to 
messages 
UK)  to  the 
ig  a  difier- 
)e  read  by 
■g  operator 
snoring  all 
nultaneous 
og  a  single 


wire,  the  number  being  Hmited  only  by  tlio  debcacy  of  the 
listener's  ear.  The  idea  of  increasing  the  carrying  power  of  a 
telegraph  wire  in  this  way  took  complete  possession  of  my  mind, 
and  it  was  this  practical  end  that  I  had  in  view  when  I  com- 
menced my  researches  in  electric  telephony. 

In  the  progress  of  science  it  i.s  universally  found  that  com- 
plexity leads  to  simplicit}',  and  in  narrating  the  history  t)f  scien- 
tific I'csearch  it  is  often  advisable  to  begin  at  the  end. 

In  glancing  back  over  my  own  researches,  I  find  it  necessary 
to  designate,  by  distinct  names,  a  variety  of  electrical  cuiTents  by 
means  of  which  sounds  can  be  ])rodueed,  and  I  shall  direct  your 
attention  to  several  distinct  species  of  what  may  be  tei'med  tele- 
phonic cuiTcnts  of  electricity.  In  order  that  the  peculiarities  of 
these  cun'ents  may  be  clearly  understood,  I  shall  ask  Mr.  Frost 


Direct 


Jntamittenti 


h,    ft 


3  yy 


i^^^Hi^k* 


d,     A 


Fig.  29. 

to  pmject  upon  the  screen  a  graphical  illustration  of  the  different 
varieties. 

The  graphical  method  of  rej>resenting  electrical  currents  shown 
in  fig.  29  is  the  best  means  I  have  been  able  to  devise  of  studying, 
in  an  accurate  manner,  the  effects  pniduccd  by  various  forms  of 
telephonic  apparatus,  and  it  has  led  me  to  the  conception  of  that 
peculiar  sjiecies  of  telephonic  current,  here  designated  as  nndula- 
tory,  which  has  rendered  feasible  the  artilicial  production  of 
articulate  speech  by  electrical  means. 

A  horizontal  line  {ij  g')  is  taken  as  the  zero  of  cnrrcnt,  and  im- 
pulses of  positive  electricity  are  I'cpresented  above  the  zero  line, 
and  negative  impulses  below  it,  or  vice  versa. 

The  vertical  thickness  of  any  electrical  impulse  {b  or  d),  mea- 
sured fi'oin  the  zero  line,  indicates  the  intensity  of  the  electrical 


54 


TIIK   SPEAKING  TELEI'HONK. 


current  at  llio  point  observed,  and  tlio  liorizontal  extension  o{ 
the  electrio  line  (b  ov  d)  indicates  tlie  duration  of  the  impulse. 

Nine  varieties  of  telejilionic  currents  may  1)0  distinfruished, 
but  it  will  only  be  necessary  to  show  you  six  of  these.  The 
three  primary  varieties  designated  as  intermittent,  pulsatory  and 
nndulatory,  are  re]U'eseuted  in  lines  1,  2  and  3. 

Sub-varieties  of  these  can  be  distinguisluul  as  direct  nr  rc- 
vei-sed  currents,  according  as  the  electrical  impidses  arc  all  of 
one  kind  or  are  alteraately  positive  and  negative.  Direct  cur- 
rents may  still  further  be  distinguishiMl  as  positive  or  negative, 
according  as  the  impulses  arc  of  one  kind  or  of  the  other. 

An  intermittent  (Hirrent  is  characterized  by  the  alternate  pres- 
ence and  absence  of  electricity  uj)on  the  circuit ; 

A  i)ulsatory  current  results  from  sudden  or  instantaneous 
changes  in  the  intensity  of  a  continuous  current;  and 

An  undulatory  cuiTcnt  is  a  cuiTcnt  of  electricity,  the  intensity 
of  which  varies  in  a  manner  proportional  to  the  velocity  of  the 
motion  of  a  particle  of  air  during  the  production  of  a  sound : 
thus  the  curve  rejircscnting  grai^hically  the  undulatory  cuiTent 
for  a  simple  musical  tone  is  the  curve  expressive  of  a  simple 
pendulous  vibration — that  is,  a  sinusoidal  curve. 


I  f 


lutermittont 


o 

o 

2$ 

~  E 


Pulsatory 


Undulatory 


Direct 


Direct 


Direct 


i  Positive     1     Positive  interniittent  current. 
( Negative   2     Negative        "  " 

Reversed  S     Reversed         "  " 


j  Positive     i 

I  Negative   5 

Reversed  G 


i  Positive 

I  Negative  8     Negative 

Reversed  9    Reversed 


Positive  pulsatory  current. 
Negative         "  " 

Reversed        "  " 

Positive  undulatory  current. 


And  here  I  may  remark,  that,  althotTgh  the  conception  of  the 
undulatory  current  of  electricity  is  entirely  ciigmal  with  myself, 
methods  of  i)rodueing  sound  by  means  of  intermittent  and  pul- 
satory cuiTents  have  long  been  known.  For  instance,  it  was 
long  since  discovered  that  an  electro-magnet  gives  forth  a  de- 


VAdKH  GALVAN'IC   MI'SIC. 


65 


cklcd  sound  when  it  is  suddenly  mafrnctized  or  demagnetized. 
Wlien  the  circuit  upon  wliich  it  is  ])]ac('(l  is  rapidly  made  and 
broken,  a  saecession  of  explosive  noises  proceeds  from  tlie  mag- 
net. These  sounds  produce  upon  the  car  the  cflEect  of  a  musical 
note  when  the  current  is  interru2)ted  a  safTuncnt  number  of 
times  per  second.  The  discovery  of  Galvanic  Music  by  Page,! 
in  1837,  led  inquirers  in  difTerent  })ai'ts  of  the  world  almost 
simultaneously  to  enter  into  the  field  of  telephonic  research ; 
and  the  acoiisti(!al  effects  produced  by  magnetization  were 
carefully  studied  by  Marrian,^  Beatson,^  Gassiot,*  Do  la 
Rive,''  Matteucci,'  Guillemin,''  Wertheim,*  AVartniann,*  Jan- 
Jiiur,!*    Joule,  ^^    Laborde,!'^   Legat,is    Reis,**  Poggeudoi-fl,  *  * 


1  C.  0.  Ihge.  "  Tlie  rroiUtctioii  oC  (ialvimio  Miisio."'  Sillimun's  .Iniiiii.,  I'iST, 
xxxii.  ji.  a'.MJ ;  Sillimuii'n  Journ.,  isay,  xxxiii.  [>.  lis  ;  Bibl.  Uuiv.  (uuw  tiurius;,  IsJJ'J, 
ii.  i<.  3'J8. 

2  J.  P.  ilarrian.  Pliil.  Mii(,'.,  xxv.  p.  3«'J  ;  Just.,  IsiS,  p.  20 ;  Aroli.  tlo  I'Klectr., 
V.  p.  J!»5. 

3  IF'.  Heatson.  Ak'Ii.  ilu  1'  Klccar.,  v.  p.  IHT  ;  Arcli.  do  So.  I'hys.  ct  Nut.  (L'd  serifs), 
ii.  p.  113. 

^    Ocueiot.     Sec  "TreatiBo  on  Kleetrlcity,"  by  Do  In  Rive,  i.  p.  300. 

"  JJe  la  Rice.  "TreiitiMU  on  Eleotricity,"  i.  p.  300;  Pliil.  Mug.,  xxxv.  p.  422; 
Aroli.  Jc  I'Kloctr.  v.  p.  'jm  ;  Inst.  ]s4il,  p.  83  ;  f'oniptes  Retx'.ds,  xx.  [i.  l-.i-'T  ;  Comp. 
Koiid.  xxii.  p.  432;  I'o^<f.  Ann.  l.xxv.  p.  637:  Ann.  du  t'Uim.  ct  do  i'hys.  xxvi. 
p.  158. 

8  Matteucci.     Inst.,  1845,  p.  315;  Areh.  dci  I'Eleetr.,  v.  SSfl. 

1  Guillemin.  Comp.  Keud.  xxii.  p.  204;  Inst.  1840,  p.  oij;  Aroli.  d.  So.  Pliy.t.  (2d 
m-ries),  i.  p.  191. 

B  G.  Wirtheim.  Comp.  Rend.  xxii.  pp.  33fi,  544;  Inst.  184fi,  pp.  66,  100 ;  I'ogpr. 
.\nn.  Ixviii.  p.  140;  Comp.  i{end.  xxvi.  p.  50,"i ;  Inst.  1848,  p.  1442;  Ann.  do  Cliim. 
ct  do  rUys.  xxiii.  p.  302 ;  Arch.  d.  Sc.  Phys.  ct  Nut.  viii.  p.  2ut> ;  Pogg.  Ann.  Ix.wii. 
p.  43;  IJcrl.  Bcr.  iv.  p.  121. 

"  Elie  Wartr/Kinii.  Comp.  Kond.  xxii.  p.  544;  Phil.  Miis.  (3d  series),  xxviii.  p. 
544 ;  Aroh.  d.  Sc.  Phys.  et  Nut.  (2d  jiea),  i.  p.  41!i ;  Inst.  l8lii,  p.  2ii0  ;  Monutsolier. 
d.Berl.  Akad.  lS4i',,  p.  111. 

10  Jannair.  Comp.  Rend,  xxiii.  p.  319;  Inst.  184ii,  p.  2ii9 ;  Arch.  d.  So.  Phys.  et 
Nut.  (2d  series),  ii.  p.  394. 

» 1  J.  J'.  Joule.     Pliil.  Mug.  .xxv.  pp.  Ii',,  225  ;  Berl.  Ber.  iii.  p.  489. 

1 8  Lahorde.    Comp.  Rend.  I.  p.  092 :  Cosmos,  xvii.  p.  514. 

IS  Legal.    Brix.  Z.  S.  ix.  p.  125 

1*  lieis.  "Telephonic."  Polytechnic  Journ.  olxviil,  p.  185;  BiUtger's  Notizhl. 
1803,  No.  0. 

IS  ■/.  C.  Ihggendorff.  Pogg.  .Vnn.  xcviii.  p.  198  ;  Berliner  .Monutsber,  1S50,  p.  133; 
Cosmos,  ix.  p.  49;  Bcr!.  Bcr.  xii.  p.  241  ;  Pogg.  Ann.  Ixxsvii.  p.  139. 


66 


TIIK   Sl'KAKlXG   TELEl'lIONE. 


Du  Monocl,!  Delozoniic'  and  otliers. '  It  should  also  be  men- 
tioned tliut  Gore*  ohtiiineil  loud  musical  notes  from  mcreury, 
ucoiinpanied  l)y  sinjfularly  beautiful  erispations  of  tlie  sur- 
face, during  the  course  of  exixiriments  in  electrolysis;  Page* 
produced  musical  tones  from  Trevelyans  bars  by  the  action  of 
the  galvanic eiu'rent ;  and  furtlicr  it  was  <liscovcn'il  by  Sullivan" 
that  iicurrentof  electricily  is  generated  by  the  vibration  of  awiro 
composed  piirtly  of  one  metal  and  partly  of  another.  The  cur- 
rent was  produced  so  long  as  the  wire  emitted  a  musical  note, 
but  stopped  immediately  upon  tiie  cessation  of  the  s^ound. 

For  several  years  my  attention  was  almost  exclusively  directed 
to  the  )>roduction  of  an  instrument  for  making  and  breaking  a 
voltaic  circuit  with  extreme  raiii<lity,  to  take  the  place  of  the 
transmitting  tuning  fork  used  in  llelmholtz'  researches.  J  will 
not  trouble  you  witli  the  description  of  all  the  various  forms  of 
ajiparatus  that  were  devised,  but  will  merely  direct  your  atten- 
tion to  one  of  the  best  of  them,  shown  in  fig.  30.  In  tlie  trans- 
mitting instrument  T  a  steel  reed  o;  is  em[)loyed,  which  is  kept 
in  continuous  vibration  by  the  action  of  an  electro-magnet  e  and 
local  Ijattery.  In  the  course  of  its  vibration  the  reed  strikes 
alternately  against  two  fixed  points  to,  I.  and  thus  eomph-tes 
alternately  a  local  and  a  main  circuit.  AVlieii  i\\r.  key  K  is 
depressed,  an  intermittent  current  from  the  main  batterv  B 
is  directed  to  the  line  wire  W,  and  passes  througli  the  electro- 
magnet Vj  ot  a  receiving  instrument  11  at  tln^  distant  end  of  the 
circuit,  and  thence  to  the  ground  G.     The  steel  reed  A  is  jilaeed 


1  Dh  Moncel.     Kxposi',  ii.  p.  l-iri;  also,  i'll.  p.  S.I. 

2  Iielezemie.     '"Souuil   produced  by   nmi^nutizatiipii,"    Mibl.  Uiiiv.  (luiw  miriu.s), 
1841,  xvi.  p.  ton. 

'  Suu  L'lndiiii  .Toiirn.  xxxii.  ]>.  402;    Polytofiliiiic  .Tourn.  c.v.  p.  in ;    Cos 

p.  4:1 ;  Gli'isciier 'I'raiti!  gem'Tul,  iV-c.  p.  :i.")ii ;   Dcivc-KpimtI.  vi.  p.  ^)^  ;  Vov 

.\Ui\.  p.  411 ;   liurl.  Hui-.  i.  p.  144;   Arch.  d.  So.  I'ljys.  ct  Nat.  xvi.  p.  40il ; 
Encj'olopicdia  dur  Pliysik,  pp.  1014-1021. 

*    ifore.     ProL'eodings  of  Koyal  Society,  xii.  p.  217. 

S    C.  G.  ruge.     "  Vibration  nf  Trovclyau'.-*  linrs  by  tlic  fralvaiiic  current. 
man's  .Tournal,  ISoO,  i.\.  pp.  10.")-los. 

«  Sullivan,     "Currents  of  Eli^ctncity  produced  liy  Ibo  vibration  ol'  .Mctid.- 
Mag.  Is45,  p.  2(il;  Arch,  du  I'jiluctr.  .\.  p.  4-0. 


ino.s,  IV. 
ir.  Ann. 
Kuiin'd 


"   Silli- 

.'•riiii. 


<li 
or 


MKL'ril'I.K   TKI,K(il{Al'IIV. 


«T 


etcd 


iplctos 
R  is 
rv  B 
ccln.'- 
)i:  the 
iliU-'cd 


smos,  iv. 

,„r,j,  Ann. 

KuUu's 


in  front  of  tlio  receiving  mugiiet,  and  wlicn  its  normal  rate  of 
vibration  is  the  sanio  as  ilio  rood  of  the  transmitting  iiistriimont 
it  is  tlirown  intopowcrfid  vil)ration,  emitting  a  mnsical  tone  of  a 
similar  pitcli  to  tliat  ])rodu(!C(l  by  tho  rwd  of  tlio  transmitting 
instrument,  but  if  it  is  normally  of  a  different  j)itoh  it  romaina 
silent 

A  glance  at  figs.  81,  32  and  83  will  show  tho  arrangement  of  fiuch 
instmmonts  ii|iou  a  tclegraphiiioireuit,  designed  to  cnablo  a  num- 
ber of  telegrai»hio  despatches  to  bo  transmitted  aimidtaneously 


Fi(j.  31). 

along  the  pamo  wire.  Tho  transmitters  and  rt'ceivers  that  are 
numbered  alike  have  the  same  \ntc\\  or  rate  ( )f  v  il  )r  it  ion.  Thus  the 
reed  of  T'  is  in  unison  witii  the  reeds  T'  and  .R'  at  all  the  stations 
n]>on  tho  circuit,  so  that  a  telegraphic  despatcli  sent  by  tho  man- 
ipulation of  tho  key  K'  at  the  station  shown  in  fig.  31,  will  bo 
received  upon  tho  receiving  instruments  li'  at  ail  tho  other 
stations  ui)on  tho  circuit.  Without  going  into  details,  I  shall 
merely  say  that  the  great  defects  of  this  j'lan  of  multiple  telc- 
gra])hy  were  found  to  consist,  firsth",  in  the  fact  that  the  receiving 
operators  were  required  to  possess  a  good  musical  car  in  orderto 
discriminate  tho  signals ;  and  secondly,  that  tho  signal?  cimld 
only  pass  in  one  direction  along  tho  line  (so  that  two  wires  wouhl 
be  Jieeesdary  in  order  to  complete  couiumuicatiou  in  both  direc- 


68 


THE   Sl'EAKXNO   TKLKPUUNE. 


1 

1 
i 

! 

\ 

\                                • 

\                                             • 

\ _'71»' 

'\ 

r 

\—^ 

r — 1 

'■ 

1    ■ 

- 

— 1 

t-  - 

'-: 

f-              '-C 

:            1 

f^r' 

1 

._ 

.  ■■'^ 

tl-^ 

.  k> 

;  i 

t^             .             '    M-l 

1 

-Jc 

■ 

— 

-fed  f* 

Er,                 * 

^^       1  1 

i 

'I- 

1 
i 

■£. 

", 

BS^M^IH 

1^    iHr? 

^  ■  II 

^^^  1  -  - 

— i' 

-  — 

■S> 


w 


VIBRATORY   CIRCUIT   BREAKER 


59 


tions).  The  first  objection  was  got  over  by  employing  the  de- 
vice which  I  tenn  a  "vibratory  circuit  breaker,"  shown  in  the 
next  diagram,  whereby  musical  signals  can  be  automatically  re- 
coi'ded. 

Fig.  84  siiov/s  a  receiving  instrument,  li,  with  a  vibratory  cir- 
cuit breaker  V  attached.  Tlio  light  s])ring  lever  V  overlaps  the 
free  end  of  the  steel  reed  A,  and  noi-mally  closes  a  local  circuit, 
in  which  may  be  placed  a  ^forsc  sounder  or  other  telegraphic 
apparatus.  When  the  reed  A  is  thrown  into  vibration  by  the 
passage  of  a  musical  signal,  the  spring  arm  V  is  thrown  upwards, 
opening  the  local  circuit  at  the  point  C.  When  the  spring  arm  V 
is  so  arranged  as  to  have  uornially  a  much  slower  rate  of  vibra- 
tiou  than  the  reed  A,  the  local  circuit  is  found  to  remain  penna- 


Fig.  u.   . 

nently  open  during  the  viliration  of  A,  tho  spring  arm  Y  coming 
into  contact  with  the  point  0  only  upon  the  cessation  of  the  re- 
ceiver's vibration.  Thus  tiie  signals  ])rod\iced  by  the  vibration 
of  the  reed  A  are  reproduced  u])on  an  ordinary  telegraphic  instru- 
ment iu  the  local  circuit. 

Fig.  .35  shows  tlie  a})])lication  of  electric  telcpl  ony  to  auto- 
graphic telegraphy,  q. '/  represent  the  reeds  of  transiuiti';.^  nistru- 
ments  of  dilTcrcnt  pitch,  s,  s  the  receivers  at  the  distant  statuMi  of 
correspcniding  pitch,  and  u,  u,  etc'.,  the  vibratory  circuit  breaki  rs 
attached  to  tlie  receiving  instrument's,  and  connected  with  meta.lic 
bristles  resting  upon  chemically  prepared  jiapcr  iv.  The  mes.sagc 
or  picture  to  be  copied  is  written  upon  a  metallic  surface,  p,  with 
non-metallic  ink,  and  placed  upon  a  meUUlic  cylinder  connected 
with  the  main  l)atterv,  c;  and  the  chemically  ])repared  paper, 
upon  which  the  message  is  to  l)e  received,  is  j^laccd  u]:)ou  a 


60 


THE   SPEAKING  TELEPHONE. 


metallic  cylinder  connected  with  the  local  battery  d  at  the 
receiving  station.  When  the  cylindera  at  cither  end  of  the  cir- 
cuit are  rotated — but  not  necessarily  at  the  same  rate  of  speed — 
a  fac  simile  of  whatever  is  written  or  drawn  upon  the  metallic 
surface^  appears  upon  the  chemically  prepared  ])apcr  w. 

The  method  by  means  of  which  musical  signids  may  be  sent 
simultaneously  in  both  directions  along  the  same  circuit  is  shown 
in  our  next  illustration,  figs.  36,  37  and  38.  The  arrangement  is 
similar  to  that  shown  in  figures  81,  32  and  33,  excepting  that  the 
interinitteut  cuiTciit  from  the  .transmitting  iustrumeuts  is  passed 


/•7f/.  :i5. 

through  the  ]inmarv  wires  of  an  indiietitm  coil,  and  the  receiving 
instruineuts  are  placed  in  circuit  with  tlie  sco  )ndarv  wire.  In  this 
way  fi'eo  cartli  communication  is  secured  at  either  end  of  the 
circuit,  and  the  musical  signals  produced  by  the  manii)ulation  of 
any  key  are  received  at  all  tlic  stations  upon  tin?  line.  The 
great  objection  to  tiiis  plan  is  the  extreme  complication  of  the 
parts  and  the  necessity  of  employing  local  and  main  batteries  at 
every  station.  It  was  also  found  by  practical  ex])erinient  that 
it  was  difficult,  if  not  iinpos.sible,  upon  either  of  tlio  jdans  hero 
shown,  to  transmit  simultaneously  th<5  number  (jf  musical  tones 


MULTIPLE  TELEGRAPHY. 


61 


62 


THE   SPEAKIXG  TELEPHONE. 


that  theory  showed  to  1)e  feusible.  Miiture  consideration  re- 
vealed the  fact  tiiat  this  diiliculty  hij  in  the  natnro  of  the  electrical 
current  cmjiloyed,  and  was  finally  obviated  by  the  invention  of 
the  undulatory  current. 

It  is  a  strange  fact  thiit  impoi'tant  inventions  are  often  made 
alrno.st  simultaneously  by  diilerent  persons  in  dillerent  parts  of 
the  world,  and  the  idea  of  multiple  telegraphy,  as  developed  in 
the  preceding  diagrams,  seems  to  have  occurred  independently 
to  no  less  than  four  other  inventoi-s  in  America  and  Europe. 
Even  the  details  of  the  arrangements  upon  circuit — shown  in 
figs.  31,  32,  33  and  36,  37,  38 — are  ex'.emoly  similar  in  the  plans 
proposed  by  Mr.  Cromwell  Varley,  of  London,  Mr,  Eiisha  Gray, 


Mg.  39. 

of  Chicago,  Mr.  Paul  La  Cour,  of  Copenhagen,  and  'Mr.  Tliomas 
Edison,  of  Newark,  New  Jei-sey.  Into  the  question  of  priority 
of  invention,  of  course,  it  is  not  my  intention  to  go  to-night 

That  the  difficulty  in  the  use  of  an  intermittent  current  may 
be  more  clearly  understood,  1  shall  ask  you  to  accompany  me 
in  my  explanation  of  the  elfect  produced  when  two  musical 
signals  of  different  pitch  arc  sinmltaneously  directed  along  the 
same  circuit.  Fig.  39  shows  an  arrangement  whcrel)y  the  reeds 
r  r'  of  two  transmitting  instrument'^  are  caused  to  interrupt 
tlic  current  from  the  same  battery,  B.  We  shall  suppose  the 
musical  interval  between  the  two  reeds  to  be  a  major  third,  in 
which  ca;c  their  vibrations  arc  in  the  ratio  of  4  to  5,  i  c,  4 
vibrations  of  r  are  made  in  the  same  time  as  5  vibrations  of  r'. 
A  and  B  represent  the  intermittent  currents  produced,  4   ini- 


MUi;iIl'I,K    'IKLKGliAl'llV. 


pulses  of  B  being  mado  in  llic  samo  tiiuo  ii.s  o  impulses  of  A. 
Tho  line  A  -|-  B  represents  tiu;  resultant  effect  upon  tlu;  main 
line  wlieu  tho  reedi^  r  and  r'  arc;  simultaneously  caused  to  make 
and  break  tho  same  circuit,  and  from  the  illustration  you  will 
perceive  that  the  resultant  current,  whilst  i-etaining  a  \iniform 
intensity,  is  less  interrupted  when  both  reeds  are  in  ojjeration 
than  when  one  alone  is  employed.  By  carrying  your  thoughts 
still  further,  you  will  understand  that  Avhen  a  large  number  of 
reeds  of  diHerent  pitch  or  of  ditl'erent  rates  of  vibration  arc  sim- 
ultimeously  making  and  breaking  tho  same  circuit,  thi'.  resuitant 
effect  upon  the  main  line  is  practically  ei[uivalent  to  <jiie  contin- 
uous current 

It  will  also  be  understood  that   the   maximuni   number  of 


Fiij.  40. 

musical  signals  that  can  be  simultaneously  directed  ahmg  a 
single  wire  without  conilict,  depemls  very  much  upon  tho  ratio 
which  the  "make"  bears  to  tho  ''break;''  tho  shorter  tho  con- 
tact made,  and  the  longer  tho  break,  the  greater  tho  number  of 
signals  that  can  be  transmitted  without  confusion,  and  vice  versa. 
The  apparatus  by  means  of  which  this  theoretical  conclusion  has 
been  verified  is  hero  to-night,  and  consists  of  an  ordinary  parlor 
harmoiiium,  the  reeds  of  which  i[ro,  operated  by  wind  in  the 
usual  manner.  In  fr(jnt  of  each  n-ed  is  arranged  a  metal  screw, 
against  which  the  reed  strikes  in  the  counso  of  its  vibration.  By 
adjusting  tho  screw,  the  duration  of  the  contact  can  bo  made 
long  or  short.  The  I'ceds  are  connect(Ml  with  one  polo  of  a 
battery,  and  the  screws  against  which  they  strike  communicate 


64 


■lllK   STEAKlNd   'J'KLEI'IIONK. 


with  tliG  line  wire,  po  that  intermittent  iinjiuLses  from  the  battery 
are  transmitted  along  the  line  wire  during  the  vibration  of  the 
reeds. 

We  now  proceed  to  tlie  next  illustration.       Without  entering 
into  the  details  of  the  calculation  you  will  see  that  with  a  pulsa- 


Fig.  41. 

tory  cuiTcnt  the  etiect  of  tran.sniitting  musical  signals  simultane- 
ously is  nearly  equivalent  to  a  continuous  current  of  minimum 
intensity — see  A  +  B,  fig.  40;  b\it  wlien  undulatory  cuiTents 
are  employed  the  effect  is  diiferent — see  fig.  41.     The  cuiTent 


Fiij.  42. 

from  the  battery  B  is  thrown  into  waves  by  the  inductive  action 
of  iron  or  steel  reeds  vibrated  in  front  of  electro-magnets  placed 
in  circuit  with  the  battery ;  A  and  B  represent  the  undulations 
caused  in  the  current  by  the  vibration  of  the  magnetized  bodies, 


tlic 

JXW 

Ihr 

usij 

en;J 

nioi 

cmj 

recJ 


Ml'I/l'ITLK   TELEOHiAPHr. 


66 


and  it  will  bo  seen  that  tliero  are  four  undulations  of  B  in  the 
same  time  as  five  undulations  of  A.  The  resultant  effect  upon 
the  main  line  is  expressed  by  the  curve  A-j-B,  whicli  is  the  alge- 
braical sum  of  the  sinusoidal  cui-ves  A  and  B.  A  similar  effect 
is  produced  when  reversal  undulatory  currents  are  employed,  as 
sbowii  in  fig.  42,  where  the  current  is  produced  by  the  vibration 
of  permanent  magnets  in  front  of  electro-magnets  united  u[)on  a 
circuit  without  a  voltaic  battery.  It  will  be  undcrstooil  from  figs. 
41  and  42  that  the  effect  of  tran.smitting  musical  signals  of  dif- 
ferent pitches  simultaneously  along  a  single  wire  is  not  to  ob- 
literate the  vibratory  character  of  the  cun'cnt,  as  in  the  case  of 
intermittent  and  pulsatoiy  currcnls,  but  to  change  the  shapes  of 


F\g.  43. 

the  electrical  undulations.  In  fact,  the  effect  ])roduced  upon  the 
current  is  precisely  analogous  to  the  effect  produced  in  the  air 
by  the  vibration  of  the  inducing  bcKlies.  Hence  it  should  be 
])ossible  to  transmit  as  many  musical  tones  simultaneou.sly 
through  a  telegraph  wire  as  through  the  air.  The  possibility  of 
using  undulatory  currents  for  the  purposes  of  multiple  telegraphy 
enabled  me  to  dispense  entirely  with  the  complicated  arrange- 
ments of  the  circuit  slunvn  in  figs.  31,  32,  33  ami  3G.  37,  38,  and  to 
employ  a  single  battery  for  the  whole  circuit,  retaining  only  the 
receiving  instruments  formerly  shown      This  arrangement  is 


66 


TIIK   Sl'EAKlXa   'l'KI,KlMIONK. 


representcMl  in  fig.  43.  Upon  viljratiug  tlio  steel  reed  of  a  re- 
ceiver 11,  11',  at;  any  .station  by  any  mechanical  means,  the  eonv- 
sponding  reeds  at  all  the  (Hlier  .stations  are  thrown  into  vibration, 
reprodncing  the  signal.  By  attaching  the  steel  reeds  to  tlie 
poles  of  a  powerful  permanent  magnet,  as  shown  in  fig.  -15,  the 
signals  can  be  produced  without  the  aid  of  a  battery. 

I  have  formerly  stated  that  Ilclmholtz  was  enabled  to  produce 
vowel  sounds  artificially  by  combining  musical  tones  of  different 
pitches  and  intensities.  His  apparatus  is  .shown  in  fig  44. 
Tuning  forks  of  different  pitch  arc  placed  between  the  poles  of 
electro-magnets  (a',  a",  &c.),  and  are  kept  in  continuous  vibration 
by  the  action  of  an  intermittent  current  from  the  fork  h.     Eeso- 


ILM 

^ 

Fi'j.UK 


nators  1,  2,  3,  eta,  are  arranged  so  as  to  reinforce  the  sounds  m 
a  greater  or  less  degree,  according  as  the  exterior  oilfices  are 
enlarged  or  contractcd, 

Thus  it  will  be  seen  tho,t  upon  Hclmholtz's  plan  the  tuning 
forks  themselves  produce  tones  of  uniform  intensity,  the  loud- 
ness being  varied  by  an  external  reinforcement;  but  it  struck  me 
that  the  same  results  would  be  obtained,  and  in  a  much  more 
perfect  manner,  by  causing  the  tuning  forks  themselves  to  vibrate 
with  different  degrees  of  amplitude.  I  therefore  devised  the 
a]iparatii3  shown  in  fig.  45,  which  was  my  first  form  of  articulat- 
ing tolophona     In  this  figure  a  harp  of  steel  rods  is  employed. 


1  The  full  (Icseriptiou  of  thU  fif^uro  v/ill  bo  fnund  in  Mr.  Aloiander  J.  EUus's 
translation  of  Ilolinholu'a  work,  "  Theory  oi  Tone." 


Miu/i'iri.K  'rKT-KonAPity. 


67 


attached  to  tlio  ixiles  of  u  jicrnianent  magm;t,  X.  S.  When  any 
one  of  tlio  rods  is  tlirowji  into  vibration  an  nnilnlatoiy  current 
is  produced  in  tlio  coils  of  the  electro-magnet  P],  and  the  electro- 
magnet E'  attracts  the  rods  of  the  harp  II'  with  a  varying  foret . 
throwing  into  vibration  that  rod  which  is  in  unison  Avith  th;.l 
vibrated  at  the  other  end  of  the  circuit  Not  only  ho,  but  the 
amplitude  of  vibration  in  the  one  will  determine  the  amplitude 
of  vibration  in  the  other,  for  the  intensity  of  tlie  induced  cuiTcnt 
is  determined  by  the  amplitude  of  the  inducing  vibration,  ami 
the  amplitude  of  the  vibration  at  the  receiving  end  depends 
upon  the  intensity  of  the  attractive  impulses.  When  wo  sing 
into  a  piano,  certain  of  tlu;  strings  of  the  instrument  arc  set  in 
vibration  S3'm})athetical]y  by  the  action  of  the  voice  with  di^.er- 


Fig.  45. 

cut  degrees  of  amplitude,  and  a  sound,  which  is  an  approxima- 
tion to  the  vowel  uttered,  is  produced  from  the  piano.  Theory 
shows  that,  had  the  jiiano  a  very  much  larger  number  of  strings 
to  the  octave,  the  vowel  sounds  would  be  j)crfectly  reproduced. 
My  idea  of  the  action  of  the  apparatus,  shown  in  fig.  45,  was 
tliis :  Utter  a  sound  in  the  neighborhood  of  the  harp  II,  and 
certain  oi  the  rods  w^ould  bo  thrown  into  vibration  with  dLffer- 
cnt  amplitudes.  At  the  other  end  of  the  circuit  the  corresj)ond- 
ing  rods  of  the  harp  U'  would  vibrate  with  their  proper  relations 
of  force,  and  the  timbre  of  the  sound  would  be  reproduced.  The 
expense  of  constructing  such  an  ajiparatus  as  that  shown  in  fig. 
45  deterred  me  from  malcing  the  attemjit,  and  I  sought  to  sim- 
plify the  apparatus  before  venturing  to  have  it  made. 

I  have  before  alluded  to  the  invention  by  my  father  of  a  sys- 


68 


TIIK   Sl'KAKlNG   TKLtl'IIONE. 


torn  of  physiolnpfiofil  pvmbols  for  roiiro?fntinrr  tlio  action  of  tlin 
vocal  f>rgaiis,  and  I  lia<l  liccii  invited  l)y  tiic  Boston  Board  of 
Kilucation  to  conduct  a  series  of  experiments  with  tlie  system  in 
the  Boston  school  for  the  deaf  and  dunil).  It  is  well  known  that 
deaf  mutes  are  dumb  merely  because  they  are  dc'if,  and  that  there 
is  no  defect  in  their  vocal  organs  to  incapacitate  them  from  utter- 
ance. Hence  it  was  tlitjuglit  that  my  fathers  system  of  pi(*torial 
syndjols,  po])ularly  known  as  visible  speech,  might  prove  a  means 
whereby  we  could  teach  the  deaf  and  dumb  to  use  their  voeal 
organs  and  to  speak.  The  great  success  of  these  ex{)crii  ats 
urged  u])on  me  the  advisability  of  devising  methods  of  exhibit- 
ing the  vibrations  of  sound  oj)tically,  for  use  in  teaching  the 


Fig.  4G. 

•leaf  and  dumb.  For  some  time  I  carried  on  experiments  with 
the  manometric  capsule  of  Kcienig  and  with  the  phonautograpii 
1  f  Leon  Scott  The  scientilic  apparatus  in  the  Institute  of  Tech- 
nology  in  Boston  was  freely  placed  at  my  disposal  for  these  ex- 
periments, and  it  happened  that  at  that  time  a  student  of  the 
Institute  of  Technology,  Mr.  Maurey,  had  invented  an  improve- 
ment upon  the  phonautograph.  He  had  succeeded  in  vibrating 
by  the  voice  a  stA'lus  of  wocjd  about  a  ft)ot  in  length,  which  was 
attaclied  to  the  membrane  of  the  phonautogra])h,  and  in  this 
way  he  had  been  enabled  to  obtain  enlarged  tracings  upon  a 
plane  surface  of  smoked  glass.     With  this  apparatus  I  succeeded 


AN    ALUAI,    I'lIOXAUTOQBAPII. 


69 


ill  producing  vorv  lieautiful  tracing.-t  of  tlic  vibrations  of  tlio  air 
for  vowel  sounds.  Sonic  of  these  tracings  arc;  shown  in  liii,  4t). 
1  was  niucli  Htriiek  witli  this  improved  form  of  apparatus,  and  it 
occurred  to  mc  that  there  was  a  rcinarkid)lo  likeness  between 
tlic  manner  in  wiiieli  this  piece  of  wood  was  vibrated  by  tlic 
mombrane  of  the  phonautograpli  and  tlic  manner  in  wliieli  the 
ussiculvu  of  the  huiuuu  car  were  iuovimI  by  tin;  tympuuic  nicin- 


/>V/.  47. 

brano.  I  determined,  tlicrefore,  to  construct  a  phonautograpli 
modelled  still  more  clo.sely  upon  the  rneclianism  of  the  human 
ear,  and  for  tliis  pnrpo.so  I  sought  the  assistance  of  a  distin- 
guished anri.^t  in  Boston,  Dr.  Clarence  .1.  Blake.  lie  suggested 
the  u.se  of  the  liumaii  car  itself  as  a  ]>hoiiautograpli,  in.<tead  of 
making  an  artificial  imitation  of  it.  The  idea  was  novel  and 
struck  mc  accordingly,  and  I  rc((uestcd  my  friend  to  prepare 


70 


THK   Sl'KAKiXa   TKLKl'HONE. 


a  specimen  for  me.  wliicli  lio  did.  IMio  iijiparatus,  as  finally  con- 
.structed,  is  .shown  in  llg.  47.  Tlui  stapes  was  iviuovcd  anil  ii. 
.stylus  of  hay  about  an  inch  in  length  was  attached  to  the  end 
of  the  incus.  Upon  moistening  the  mend>rana  tympani  and  the 
ossiculas  with  a  mixture  of  glycerine  and  water  the  necessary 
mobility  of  the  parts  was  obtained,  and  upon  singing  into  the 
external  artificial  car  the  .stylus  of  hay  was  thrown  into  vibration, 
and  tracings  were  obtained  upon  a  piano  surface  of  smoked 
glass  jiassed  rapidly  underneath.  While  engaged  in  these  (>\- 
pcriments  I  was  struck  with  the  remarkable  disproportion  in 
weight  between  the  membrane  atid  the  bones  that  were  vibrated 
by  it  It  occurred  to  me  that  if  a  membrane  as  thin  as  tiss\ie 
paper  could  control  the  vibration  of  hones  that  were,  compared 
to  it,  of  immense  size  and  weight,  why  should  not  a  larger  and 
thicker  membrane  be  able  to  vibrate  a  piece  of  iron  in  front  of 


an  electro-magnet,  in  which  case  the  complication  of  steel  rods 
show^n  in  my  first  form  of  telephone,  fig.  45,  covild  bo  done 
away  with,  and  a  simple  piece  of  inm  attached  to  a  membrane 
be  placed  at  cither  end  of  the  telegraphic  circuit. 

Fig.  48  shows  the  form  of  apparatus  that  I  was  theit  employ- 
ing for  producing  undulatory  currents  of  electricity  for  the  pur- 
j)oses  of  multiple  telegra])liy.  A  steel  reed.  A,  was  clamjjcd 
firmly  by  one  extremity  to  the  uncovered  leg  h  of  an  electro- 
magnet E,  and  the  free  end  of  the  reed  projected  above  th(> 
covered  leg.  When  the  reed  A  was  vibrated  in  any  mechanical 
way  the  battery  current  was  thrown  into  waves,  and  electrical 
undulations  travci-sed  the  circuit  B  K  W  E',  throwing  into  vibra- 
tion the  corresponding  reed  A'  at  the  other  end  of  the  circuit. 
I  immediately  proceeded  to  i)ut  my  new  idea  to  the  test  of 
practical  experiment,  and  for  this  purpose  I  attached  the  reed 


bell's  INOPEKATIVE  TE1RT.H0NK. 


71 


A  (fig.  49)  loosely  by  one  extremity  to  the  uncovered  polo  h  of 
tlio  mag!ict,  uiid  fastened  the  other  extremity  to  the  centre  of  a 
stretched  membrane  of  goldbeaters'  akin  n.  I  ]iresuinc(l  that 
upon  speaking  in  the  neighi)orhood  of  the  membrane  nit  would 
be  thrown  into  vibration  and  cause  the  steel  reed  A  to  move  in 
a  similar  manner,  occasioning  undulations  in  the  electrical  cur- 
rent that  would  corres])ond  to  the  changes  in  the  density  of  the 
air  during  the  production  of  the  sound ;  and  I  further  thought 
that  the  change  of  the  intensity  of  the  current  at  the  receiving 
end  would  cause  the  magnet  there  to  attract  the  reed  A'  in  such 
a  manner  that  it  should  copy  the  motion  of  the  reed  A,  in  which 
case  its  movements  woiUd  occasion  a  sound  from  the  mendirane 
n'  similar  in  timbre  to  that  which  had  occasioned  the  original 
vibration. 


Fig.  49. 

The  results,  however,  were  unsatisfactory  and  discouraging. 
My  friend,  Mr.  Thomas  A.  Watson,  who  assisted  me  in  this  iirst 
experiment,  declared  that  lie  heard  a  faint  sound  proceed  from 
the  telephone  at  his  end  of  the  circuit,  but  I  was  unable  to 
verify  his  assertion.  After  many  experiments,  attended  by  the 
same  only  partially  successful  result.'^,  I  determined  to  reduce 
the  size  and  weight  of  the  spring  as  much  as  possible.  For  this 
purpose  I  glued  apiece  of  clock  spring,  about  the  size  and  shape 
of  my  thumb  nail,  firmly  to  the  centre  of  the  diaphragm,  and 
had  a  similar  instrument  at  the  other  end  (fig.  50) ;  we  wen; 
then  enabled  to  obtain  distinctlv  audible  effects.'     I  remember 


'  On  tho  14th  of  February,  ISiTj,  Mr.  Klisliii  Crniy,  of  Chictt(,'o,  filed  ii  cuvoat  in 
the  Patent  OfHcu  at  Washington,  Joscribing  tlie  Spualviiig  Telephone  shown  in 
flgiirc  Ii,  page  15,  and  which,  npon  examination,  will  \n:  found  to  be  identical  witli 
lluit  shown  in  fiirures  f.O  and  U'l.  On  the  Haiiic  day  Professor  Rell  filed  an  applica- 
tion in  the  Patent  Ollicu  at  Washington,  Ueseribing  the  apparatus  shown  in  liguro 


72 


THK   SPEAKING   '1  KLEPlloNi:. 


an  cxn.  rimjiit  in;i(le  with  this  telephone,  which  ;it  tlio  time  gave 
me  givat  .viiiskctioii  ami  delight  Quo  of  tlic  telephones  was 
I'htced  in  ii'y  lecture  room  in  tiio  Boston  University,  and  the 
other  in  the  basement  of  the  adjoinin<r  building.  One  of  my 
stud(Mits  repaired  to  the  distant  t(>le])hon(!  to  oljserve  the;  elTects 
of   articulute   speech,   'vhile  1   uttered   the  sentence,    'Do  yuu 


Firj.  50. 


understand  what  I  say?'  into  the  tele]>hone  placed  in  the  lecture 
hall.  To  my  delight  an  answer  was  returned  through  the  in- 
struinc-' *■  itself,  articulate  sounds  ])roceeded  fn^m  the  steel  spring 
attach('(l  to  the  membrane,  and  I  heard  the  sente-iee,  "Yes,  I 
understand  you  ])erfeetly  "     It  is  a  mistake,  however,  to  suppose 


/"(■;/ .  Tii. 


that  the  articulation  was  l)y  any  means  jierfect,  and  expectanev 
no  douL*  had  a  great  deal  to  do  with  my  recognition  of  the 
sentence;  still,  the  articulation  M-as  there,  and  I  recognized  tiic 
fact  that  the  indistinctness  was  entirely  due,  to  the  imperfection 
of  the  instrument.     I  will  not  trouble  you  by  detailing  the 


49,  wliicli  lie  horci  aekiiowlodges  would  not  work,  mid  it  was  not  until  after  ho  ha.i 
substituted  tlie  apparatus  shown  in  Mr.  Grav'^"  ••avcat  in  iilare  of  it.  tliat  hr  wis 
enulih'd  to  suceessfull.v  acconiplisli  the  (rrand  ohjuot  of  reproducing  urticulate 
Hpeceh  at  a  distuuue.     See  note,  i)a^'e  Tv.— G.  13.  I'. 


fJKAYS  TELKPIIONIC   TKAXSMrrj'ER.  73 

various  stages  tlirough  wliicli  ihe  jipparatu;-;  missed,  Imt  shall 
merely  say  that  after  a  time  I  j)n)duee(l  the  form  of  instrument 
tiliDWii  in  fig.  61,  wliieii  served  wry  \yo\\  as  a  receiving  lele- 
plione.  ]ii  this  ecndition  my  invention  was  exhibited  at  the 
Centennial  Kxhihition  m  Philadelphia,  The  telephone  shown  in 
fig.  50  was  iisecl  as  a  transQiittiiig  instrument,  and  that  in  fig.  51 
as  a.  reeeiver,  so  that  vocal  couimuiueatiou  was  only  established 
ni  oiu!  direction. 

An(jther  fonn  of  Iransmitting  teie])hone  exhil)itcd  m  Phila- 
<lel])hia,  intiMuled  for  use  with  the  receiv''ig  telejjhone  (fig.  51), 
IS  represented  by  lig.  52. 

A  platinum  wire  attached  to  a  stretched  membrane  completed 
a,  voltaic  circuit  by  di])ping  into  water.'      L'pon  sjjeaking  to  the 


membrane  artienlatc  .sounds  jiroceeded  from  the  telephone  in  the 
distant  room.  The  sounds  pi-oduced  by  the  telephone  became 
louder  when  dilute  sul])huri('  acid,  or  a  saturatiMl  solution  of  .salt, 
was  sui]stitute(l  for  the  water.  Auoible  effecls  were  al.^^o  ]'iro- 
<lueed  by  the  vibration  of  ])lumbago  in  mercury,  in  a  solution 


'  From  the  ri>ndin(?  of  the  tc.\t  it  iniplit  bo  erroneniisly  int'iiri>il  thiit  the  iippiirntu."* 
hIiowm  in  iijfuri;  52  was  invented  by  I'rot'es.sor  Boll,  and  exhibited  by  hmi  ut  tho 
i'eiiteiinial  Exhibition.  Priilehsor  Bell  neither  invented  nor  exhibited  it.  Tho 
iilxive  fiirure  rein'eseiitu  tlio  tri'iisiiiittinLf  porti'in  of  Eli.-ilia  Gray'n  oriirinal  Speakiiii; 
Telei>hcini'  -  the  tirst  articiilatintr  ti'lephono  ever  invented.  Tlie  eonipli  te  apparatus 
iH  sliown  in  tiirnro  <1,  jiane  1.''.  Mr.  (iniy  exporinieiited  with  his  telepliono  at  the 
Oentennial  Exhiiiition  at  IMiilu(lel|)hia  in  l^V<i,  and  sliowed  it  to  Koine  of  liis  friends, 
nnioiiir  others  to  I'rofessor  Harker, 'jf  tho  University  of  I'eunsylvania,  but  did  not 
axliibit  it  to  tho  .ludifos. — G,  B.  1', 


i 


74 


THE   SPfCAKiXO  TELEPHONE. 


of  hichromato  of  potash,  in  suit  and  water,  in  dilute  sulphuric 
acid,  and  in  pure  water. 

The  articulation  j)roduced  from  the  instrument  shown  in  fig. 
51  was  remarkably  distinct,  hut  its  great  detect  consisted  in  the 
fact  that  it  could  not  he  used  as  a  transmitting  instrument,  and 
thus  two  telephones  were  retjuirecl  at  each  station,  one  for  trans- 
mitting and  one  for  i-eceiving  jpoken  messages. 

It  was  determined  to  vary  the  construction  of  the  telcjihone 
shown  in  tig.  50,  and  I  r.ought,  liv  c-hanging  the  size  and  t(Misi()n 
of  tlic  membrane,  the  diameter  and  thickness  of  the  steel  spring, 
the  size  and  power  of  the  magnet,  and  the  c<jils  of  insulated  wire 
around  their  poles,  to  discover  empirically  the  exact  effect  of 
each  element  of  the  combination,  and  thus  to  deduce  a  more  ])rr- 
fect  form  of  a[jparatiis.     .It  ^^^^^  found  that  a  marked  increase  iu 


Fig.  63. 

the  loudness  of  the  sounds  resulted  from  shorteninp  the  length 
of  tlie  coils  of  wn-e,  and  by  enlarging  the  iron  diaphragm  which 
was  glued  to  the  membrane.  In  the  latter  case,  airo,  the  dis- 
tinctness of  the  articulation  was  improved.  Finally,  the  mem- 
brane <.)f  gold  beater.s'  k'n  was  discarded  jutirely,  luid  a  simple 
iron  plate  was  used  instead,  and  at  o\u:c  intelligiblo  articulation 
was  obtiiined.  ^I'lie  new  form  of  instrument  is  that  ;  hown  in 
fig.  53.  and,  as  had  been  long  anticipated,  it  was  ])r(jved  that  the 
only  u.se  of  the  battery  was  to  magnetize  the  iron  core  of  the 
magnet,  for  the  effects  were  ocpially  audible  when  the  battery- 
was  omitted  and  a  rod  ot  magnetijied  steel  substituted  for  the 
iron  core  of  the  magnet 
I    It  was  my  original  intention,  as  shown  in  lig.  45,  and  it  was 


.I.„ 


DOLBKAR'S   MAGNETO-ELECTIilC  TELEPHONE. 


f  always  claimed  by  mc,  that  tlio  final  fonn  of  tclephono  woul 
be  operated  by  2)ermaneiit  magnets  in  i)lace  of  batteries,  and 
numcronw  e\i)eriincntM  had  been  carried  on  Ity  Mr.  Watson  and 
myself  j)rivately  for  the  ])urpose  of  producing  this  efTcct 

At  the  time  the  instruments  were  llrst  exliibitc<l  in  juiblic  tlie 
results  obtained  with  pennanent  magnets  were  not  nearly  so 
striking  as  wluni  a  voltaic  battery  was  employed,  wherefore  we 
thotight  it  ])e.st  to  exhibit  <Mdy  the  latter  forni  of  instrument. 
j  The  interest  excited  by  the  first  published  accounts  of  the 
I  operation  of  the  teleplione  led  many  ]>ci.^ons  to  investigate  tlie 
I  subject,  an<l  1  doubt  not  that  numljers  of  c.xpcrimcntei'S  have 
I  indcpend(Mitly  discovered  tliat  ])ermanent  magnets  might  be  em- 
\  ]iloyc<l  instead  of  voltaic  batteries.  Indceil,  one  gentleman. 
Professor  Uolboar,  of   Tufts  College,  not  only  claims  to   have 


'"a 

,1.1?  3 


/  Pi'J.  54.  I 

\  disoovered  the  ma.Erneto-clectric  telephone,  but,  I  understand, 
j  <'liargcs  me  with  having  obtained  tlic  idea  from  him  through  the 
(  medium  of  a  nmtual  friend. 

A  still  more  powerful  form  of  apparatus  was  constructed  Ijy 
using  a  powerful  compound  hoi"se  shoe  magnet  in  jilace  of  the 
straight  rod  which  liad  been  previcjuslv  used  (see  fig.  54).  In- 
deed, the  sounds  })roduced  by  means  of  this  instrument  were  of 
sufficient  loudness  to  be  faintly  uudible  to  a  large  audience,  and 
in  this  condition  the  instrument  was  exhibited  in  the  Essex  In- 
stitute, in  Salem,  Massachusetts,  on  the  12th  Keltrunry,  1877,  on 
which  occasion  a  short  speech  shouted  into  a  similar  telephone 
in  Mo.ston,  sixteen  miles  away,  was  heard  by  the  audience  in 
Salem.  The  tones  of  the  si)eaker's  voice  W(>n'  distinctly  audible 
to  an  audience  of  six  hun<lrcd  "-^ople,  but  the  articulation  was 


70 


THE   SPEAKING   TELEPHOXE. 


only  distinct  iit  a  distiincc  of  about  six  foot.  On  tlic  same  occa- 
sion, also,  a  report  of  tlio  lecture  was  transmitted  liy  word  of 
iiioiith  from  Sa'em  to  Boston,  and  [lublislied  m  the  i)apors  the 
next  morning. 

From  tlie  form  of  telephoiK^  shown  in  lig.  53  to  the  present 
form  of  tlie  instrument  (lig.  55)  is  hut  a  .stcj).  It  is,  in  fact,  the 
arrangement  of  iig.  63  in  a  portable  form,  the  magnet  F  II  being 
2)laccd  inside  the  liaudio  and  a  more  convenient  form  of  mouth- 
piece provided.  The  arrangement  of  these  in.struments  upon  a 
tel('gi"a[ihic  eii'euit  is  shown  in  lig.  50. 

And  hero  I  wi.-<li  to  express  my  in(h'l)tedness  to  several  scien- 
tilie  friends  in  America  for  1  heir  cooperation  and  assi.stance.  1' 
v'ould  s|)ecially  mention  Professor  Peirco  and  Professor  Blake, 
of  Brown  University,  Dr.  Clianuing,  Mr.  Clarke  and  Mr.  Jones. 
In  Providence,  Rhodo  Island,  these  gentleman  have  been  carry- 
ing on  together  ex[)eriments  seeking  to  perfect  the  form  of  fip- 
]>aratns  required,  and  I  aiu  ha])py  to  reconl  the  fact  that  they 
(•(Uninnnicated  to  me  each  now  discovery  as  it  was  made,  and 
eveiy  new  step  in  their  investigations.  It  was,  of  course,  almo.sti* 
inevitable  that  these  gentlemen  should  retrace  much  of  the  ground 
\  that  had  been  gone  over  by  me,  and  so  it  has  happened  that 
I  many  of  their  discoveries  had  b<'(>n  anticipated  by  my  own  re- 
searches ;  still,  the  very  hoiinraliKj  way  in  which  they,  from  time 
to  time,  placed  before  mo  tlie  I'osults  of  their  discoveries,  entitles 
them  to  my  warmest  thanks  ami  to  my  highest  esteem.  It  was 
always  my  belief  that  a  certain  I'atio  would  be  found  Ix'tween 
the  several  parts  of  a  telephdne.  and  that  the  size  of  the  instru- 
rnont  was  inunaterial  ;  but  Professor  Poircc  was  the  first  to  de- 
mcmstrati!  t\\o  extreme  smalluess  oi  the  magnets  which  might  1)(> 
em])loyed.  And  lu're,  in  order  to  show  the  parallel  lines  ni 
which  W(!  wer(^  working,  I  ma\'  mention  the  fact  that  two  or 
thi'ee  days  after  I  had  constructed  a  tele|ihone  of  the  jiortable 
form  (lig.  55),  containing  the  magnet  inside  the  handle,  Dr. 
Chainiing  was  kind  (Miougli  to  send  me  a  pair  of  telephones  of 
a  siniil.ir  pait^'rn,  which  had  been  invented  by  the  Pro\-i(li^nce 
experimenters.     The  eonveuunt  form  of  mouthpiece  shown  m 


c 

tl 


I'EIUCES   TELEl'IIONK    MOUTHI'lliCl-;. 


77 


i\'j.  55,  now  iulopted  by  lac,  was  iuveiitod  .solely  by  iny  friend, 
Pvofessor  Peirfo.  I  must  also  express  my  oblii'-atioiis  to  my 
frii'iiil  and  associate,  Mr.  Tlioimis  A.  Watson,  of  .Salem,  Massa- 
ehusetts,  who  has  for  two  years  past  given  ine  his  pereonal  assist- 
ance in  carrying  on  my  researches. 

In  pursuing  my  investigations  I  have  ever  had  one  end  in 
view — the  practical  improvement  of  electric  telegraphy — but  I 
have  eotae  across  many  facts  which,  while  having  no  direct  bear- 
ing upon  the  subject  of  telegra])hy,  may  yet  pcjssess  an  interest 
for  you.  * 

/  For  instance,  I  have  found  that  a  musical  tone  ])roceeds  from 
a  piece  of  ])lumbag(j  or  retort  carbon  when  an  intermittent  cur- 
rent of  electricity  is  passeil  through  it,  and  I  have  observed  the 

^  most  curiiKis  audible  elfcH'ts  produced  by  the  passage  of  reversed  | 
intermittent  currents  through  the  human  body.  A  rheotome 
was  placed  in  circuit  with  the  ])rimary  wires  of  an  induction  coil, 
and  the  line  wires  were  connected  with  two  strips  of  brass.  One 
of  these  strips  was  held  closely  against  the  ear,  and  a  loud  sound 
[)roceeded  fi'om  it  whcncvei'  the  other  slip  was  touelied  with  the 
other  liand.  Tiie  stri])s  of  brass  were  ne.xt  held  one  in  eacli 
hand.  "  The  induced  (nirrents  occasioned  a  muscular  tremor  in 
the  iingci's.  Upon  placing  my  fordinger  to  my  ear  a  loud 
crackling  noise  was  amlible,  seemingly  proceeding  from  the  lin- 
ger itself.  A  friend  who  was  }jresent  ])laced  my  linger  to  his 
ear,  but  heard  nothing.  I  requested  him  to  hold  the  strips  him- 
.self.  lie  was  the  listinctly  cor  icious  of  a  noise  (which  I  was 
unable  to  perceive)  proceeding  from  his  linger.  In  this  case  a 
portion  of  the  induced  currents  jjassed  through  the  head  of  the 
observer  ■<  "n  he  ]/K.ced  his  ear  against  his  own  linger,  and  it 
is  possib'  rhat  the  sound  was  occasioned  by  a  vibration  of  the 
surfaci's  ..f  the  ear  and  linger  in  contact. 

When  two  per.=i-ns  receive  a  shock  from  a  RuhmkorlT's  coil  by 
clasjjing  hands,  ^.ach  taking  hold  of  one  wire  of  the  coil  with 
the  free  hand,  a  st)und  proceeds  from  tlie  cliisped  lumda    'i'lie 


^, 


1  f^co  liesearcheg  in  Telephony.    Trons.  of  .\inerionti  Aoud.  of  Arts  iinJ  Scioiioos, 

vol.  xii.  ]).  1, 


78 


THE   SPKAKING   TELEPHONE. 


effect   is   not   produced   when    the   hands   uro    moist.       Wlion 
either  of  the  two  touclics  the  body  of  the  otlier  u  li^nd  sound 
comes  from  the  parts  in  contact      Wlien  the  arm  of  one  is 
])laced  against  the  ai'ui  of  the  otlicr,  tlie  noise  proiluced  can  be 
heard  at  a  distance  of  several  feet     In  all  these  cases  a  sliglit 
shock  is  experienced  so  long  as  the  contact  is  preserved.     The 
intro(hiction  of  a  piece  of  paper  between  the  parts  in  contact 
does  not  materially  interfere  with  the  pnjduction  of  the  sounds, 
but  the  unj)leasant  effects  of  the  shock  are  avoided. 
/        When  an   intermittent   current  from  a  liuhndcorff's  coil  is 
)    passed  through  the  arms   a    musical    note  can   be    perceived 
i^   I     when  the  ear  is  closely  applied  to  the  arm  (^f  the  person  experi- 
\    mcntcd  upon.     The  .sound  seems  to  proceed  from  the  muscles  of 
the  fore-arm  and  from  the  biceps  muscle.     IMr.  Elisha  Grayi  has 


5 


Fig.  ftS. 
also    produced   audil^h*   clTt-etx    bv    the   pa-sage    of    electricity 
through  the  hunijiu  bod  v. 

An  extremely  loud  nuisical  r>>te  is  occasioned  })y  the  spark  of 
a  Ruhmkorff's  coil  when  the  primary  circuit  is  made  and  broken 
with  sufficient  rapidity.  When  two  rheotomes  of  different  pitch 
are  caused  simultuieously  to  open  and  close  the  primary  circuit 
a  double  tone  proceeds  from  the  spark. 

A  curious  discovery,  which  may  be  of  interest  to  yon,  has 
been  made  by  Professor  Blake.  lie  constructed  a  telephone  in 
which  a  rod  of  soft  iron,  about  six  feet  in  length,  was  used 
instead  <if  a  ])ermanent  magnet  A  friend  sang  a  continuous 
musical  tone  into  the  mouthpiece  of ;   telephone,  like  that  shown 


1  Elisha  Oral/.    Eiig.  Pttt.  Spec,  No.  a«40,  Aug.,  1874. 


ULAKES  TELEPHOXIC   EXPEHIMENTS. 


7!» 


in  iifr.  55,  wliicli  was  connoeted  with  tlio  soft  iron  instninient 
alluded  to  ;d)ove.  It  was  found  tliat  the  loudness  of  tlie  sound 
produced  in  this  trlc])]i(ine  varied  with  the  direction  in  which 
tlio  iron  rod  was  licld,  and  that  the  niaxiniuin  cilect  was  ])ro- 
duccd  when  the  nxl  was  in  the  position  of  tlic  dipping  needle. 
This  curious  discovery  of  Professor  Blake  has  Leen  verified  by 
myself. 

When  a  telephone  is  placed  in  circuit  with  a  tclcgi'a]»h  line 
the  telephone  is  found  scetningly  to  emit  sounds  on  its  own 
aeeount.  Tlie  most  extraordinary  noises  ai'e  often  iiroduccd,  the 
causes  of  which  arc  at  present  very  obscure.  One  cLkss  of 
sounds  is  p 'oduced  by  the  inductive  intluence  of  neighboring 
Avires  and  by  leakage  from  thcni,  the  signals  of  the  Morse 
alphabet  passing  over  neighboring  wires  being  audible  in  the 
telej)hone,  and  another  class  can  l)c  traced  to  earth  currents  ujwn 
the  wire,  a  curious  modification  of  this  sound  revealing  the 
presence  of  defective  joints  in  the  wire. 

Profes.sor  Blake  informs  me  that  he  has  been  able  to  u.se  the 
railroad  track  fur  convci'sational  purposes  in  place  of  a  tele- 
graph wire,  and  he  further  states  that  when  only  one  telephone 
was  connected  with  tlie  track  the  sounds  of  Morse  operating 
were  distinctly  audible  in  the  telephone,  although  the  nearest 
telegraph  wires  were  at  least  forty  feet  distiint 

Pn^fcs-sor  Peirce  has  observed  the  most  curious  sounds  pro- 
/  duced  from  a  telephone  in  conncctitm  Avith  a  telegraph  wire 
I  during  the  aurora  borealis,  iiml  I  have  just  heard  of  a  curious 
phenomenon  lately  observed  by  Dr.  Channing.  In  the  city  of 
Providence,  Rhode  Island,  there  is  an  (.)verhouse  wire  about  one 
Tnile  in  extent  with  a  telephone  at  either  end.  On  one  occa.sioii 
tlie  sound  of  music  and  singing  was  faintly  audible  in  one  of 
the  tcli'phonos.  It  secmc(l  as  if  some  one  was  practicing  vocal 
music  witli  u  ])ianoforte  accompaniment.  The  natural  supposi- 
tion was  that  experiments  were  being  made  with  the  telephone 
at  the  other  end  of  the  circuit,  but  n[>on  impiiry  this  proved  not 
to  have  jeen  the  case.  Attention  having  thus  bceti  directed  to 
the  phenomenon,  a  watch  was  kept  \ipon  tlu>  instruments,  and 


6U 


THK   SPEAKING   TELEPHONE. 


npnn  a  sniisoqnont  occnsion  tlio  samo  fact  was  ohsorvod  at  both 
cuds  of  the  lino  \>y  Dr.  Cluimiing  ami  liis  friends.  It  was  prov^od 
that  tlio  sounds  oontinuod  for  al)oiit  two  hours,  and  usually  com- 
menced about  tlie  same  time.  A  .searching  examination  of  tin; 
hue  disclosed  nothing  abnormal  in  its  condition,  and  I  am 
unable  to  give  you  any  explanation  of  this  curious  phenomenon. 
Dr.  Chauning  has,  however,  addressed  a  letter  u])()n  the  subject 
to  the  editor  of  one  of  the  Providence  pajjcr-s,  giving  the  names 
of  such  .songs  as  were  recognized,  with  full  details  of  the  obser- 
vations, in  the  hope  that  ])ublicity  may  lead  to  the  discovery  of 
the  performer,  and  thus  aflord  a  .solution  of  the  rnj'stery. 

My  friend  Mi;  Fredcric^k  A.  Gower  communicated  to  me  a 
curious  obst'i'vation  made  by  him  regarding  the  slight  earth  con- 
nection required  to  establish  a  circuit  for  the  telephone,  fmd 
together  we  carried  on  a  series  of  experiments  with  rather  start- 
ling results.  We  tooic  a  coujDle  of  telephones  and  an  insulated 
wire  aliout  100  yards  in  length  into  a  garden,  and  were  enabled 
to  carry  on  conversation  with  the  greatest  ease  when  we  held  in 
our  hands  what  should  liave  been  the  earth  wire,  so  that  the  con- 
nection with  the  ground  was  formed  at  cither  end  through  our 
bodies,  our  feet  being  clothed  with  cotton  socks  and  leather 
boots.  Tlie  day  was  fine,  and. the  grass  uj)on  which  we  stood 
was  .seemingly  perfectly  dry.  Upon  standing  upon  a  gravel 
walk  the  vocal  sounds,  though  much  diminished,  were  still  per- 
fectly intelligible,  and  the  same  result  occurred  when  standing 
upon  a  bri<;k  wall  one  foot  in  height,  but  no  sound  was  audible 
when  one  ot  us  stood  upcin  a  block  of  freestone. 

One  experiment  which  we  made  is  so  very  interesting  that  I 
must  speak  of  it  in  detail.  Mr.  Gower  made  earth  connection 
at  his  end  of  the  line  by  .standing  upon  a  gra.ss  plot,  whilst  at 
the  other  end  of  the  liiKs  I  stood  upon  a  wooden  board.  [  re- 
quested Mr.  Gower  to  sing  a  continu(;us  musical  note,  and  to 
my  surpri.se  the  .sound  was  very  distinctl>  audible  from  the  telc- 
[thone  in  my  hand.  LIpon  examining  my  feet  I  discovered  tha.t 
a  single  blade  of  grass  was  bent  over  the  edge  of  the  board,  and 
that  my  foot  touched  it.     The  removal  of  this  blade  of  grass 


PHKECKH   TKLKl'IloNIC   OHSKUSATIONS. 


81 


was  followed  liy  tin;  cossatiou  of  tli(!  sound  from  the  tcleplionc, 
and  1  found  that  tlu!  moment  I  touelied  with  the  toe  of  my 
l)oot  a  l)la(lc  of  f^niss  or  tlie  petal  of  a  daisy  the  smnid  was 
ag'ain  aiulible. 

The  quostion  will  naturally  arise.  Throu^di  what  lenuth  of 
wire  can  the  telephone  he  used?  In  reply  to  this  [  may  say 
that  the  maximum  amount  of  resistance;  tln'ouLdi  which  the  un- 
dulatory  current  will  ]iass,  mid  yet,  retain  sudieient  force  to  pro- 
duce an  auilil)le  soun<l  at  the  distant  end,  has  yet  to  be  deter- 
mined;  no  difliculty,  has,  however,  lieen  experienced  in  labora- 
tory experiments  in  eonversiu!^;  thi'iHiuh  a  resi.staneo  of  60,000 
nhms.  which  has  been  the  maximum  at,  my  di.spo.sal.  On  ou(! 
(Ktcasion,  not  havinjx  a  rheostat  at  hand,  1  may  mention  having' 
passed  tlio  current  thronji,h  the  bodies  of  sixteen  perstms,  who 
stood  liand  in  hand,  "^riie  longest  liMitrth  of  real  tele;jrra])h  line 
through  which  I  have  attempted  to  converse  has  bt.rn  about  250 


|G|  I G| 

Fi'j. .-.(;. 

miles.  On  this  occasion  no  diiriculty  was  experienced  .<o  long 
as  parallel  lines  wen;  not  in  operation.  Sunday  was  cho.sen  as 
the  day  on  which  it  was  pi'obabic  other  circ'uit.s  would  In;  at 
rest.  Conversation  was  carried  on  bi^twecn  mvself,  in  New 
York,  and  Mr.  'J'homas  A.  Watson,  in  IJoston,  until  tlu;  opening 
of  ])usiness  upon  the  othci-wires.  ^Vheu  this  [ia|)[)ened  the  vocal 
soiuuLs  were  very  much  diminished,  but  still  audible.  It  seemed, 
indeed,  like  talking  through  a  storm.  Conversation,  though  pos- 
sible, could  be  carried  on  with  diOieulty,  owing  to  the  distructing 
n.'iture  of  the  interfering  current.s. 

-  1  am  informed  by  niv  friend  ^[r.  Precee  that  conversation  has 
been  successfidly  carrietl  on  through  a  submarine  cable,  sixty 
miles    in  leniilh,   extendinti;  from    Dartmouth  to   the  Island  ol 


82 


THE   SPEAKING  TELEPHONE. 


Gnornscy,  l)y  ineuns  of  hand  trii  nlioiu's  similar  t.(^  tiuit  sliown 
in  lig.  66.'' 

At  tlio  conclusion  of  tlie  lecturo  cnnipliincnt  irv  remark's  were 
made  liy  tlio  President  and  various  ntlici'  members  who  were 
ju'esent,  and  ;i  cordial  vote  of  thanks  was  extended  to  Professor 
Bell  for  his  very  philosophical  and  entertaining  discourse.  We 
reproduce  a  ])ortion  of  the  remarks  made  ]>y  Mr.  Preece  : 

"  Wiiilc  on  the  one  part  Professor  Bell  has  placc(I  in  our 
hands,  to  a  certain  extent,  a  new  power,  lie  has,  on  the  <)th(>r 
hand,  thrown  upon  our  shoulders  an  extra  weight.  The  poor 
telegraph  engineer  has  now  to  master  many  .sciences.  Not  only 
must  he  know  something  of  electricity  and  magnetism — notonly 
must  he  know  a  good  deal  of  chemi.stry — not  ordy  must  lie  |)ass 
through  various  stiiges  of  mathematical  knowledge,  hut  now, 
thanks  to  Professor  Bell,  he  is  ohliged  to  he  master  of  the  in- 
tricacies of  acoustics.  I  do  not  blame  him,  because  the  study 
of  .«o)md  is  in  itself  a  beautiful  occupation,  and  when  it  becoines 
linked  to  one's  profession  it  becomes  almo.st  a  luxury. 

Professor  Bell  alluded  to  the  ^act  that  ex])cctancy  led  him  in 
his  first  teleplume  to  anticipate  what  was  said.  I  will  give  you 
an  illu.stration  of  the  effect  of  expectancy.  It  was  my  pleasure, 
on  a  recent  occasion,  to  exhibit  the  telephone  before  a  very  large 
audience.  Many  learned  men  were  present  There  is  one  very 
remarkable  feature  of  a  learned  meeting.  When  you  call  u])on 
a  learned  member  to  make  a  learned  remark  he  frequently 
malces  a  foolish  one.  Now,  I  selected  one  of  the  leading  scien- 
tific men  of  the  day,  and  placed  the  telephone  in  his  hand.  It 
was  in  connection  with  a  similar  instrument  fifty-five  miles 
away.  Of  couree  we  expected  to  h<!ar  from  him  some  learned 
axiom,  some  sage  aphori.sm  or  some  wonderful  statement ;  but, 
after  some  hesitation,  he  said  :  '  Iley  diddle  diddle — follow 
that  up.'  lie  rapidly  put  the  telephone  up  to  his  ear  and  an- 
nounced with  much  glee,  'lie  says,  cat  and  the  liddle.'  Fifty 
miles  off  my  assi.stant  was  answering  the  question.  I  asked  him 
next  day  if  he  understood  'Iley  diddle  diddle.'  He  said  'No." 
'  What  did  3011  say '/'     ' I  asked  him  to  rei)eat !'  " 


an 
Tl 
an 
ev 


CIIAP'PEIi  TTL 


TUK   TKl.KI'llDNK    .\|il!t>AI). 


1  Of  all  modern  iiivontioiis  coiinccteil  with  the  transmission  of 
telegnipliic!  signals,  the  tek-phoiii',  devised  l)y  Mr.  Alexander 
<iraliaui  liell,  has  exeited  the  most  widespread  interest  and  w(Mi- 
di'r.  Wherever  Mr.  Bell  has  appeared  before  the  pnblio  to  give 
an  account  of  his  invention  and  tlie  researches  whieli  have  led 
up  to  it,  crowds  have  assembleil  to  hear  him.  Nor  is  this 
astonishing;  for  the  telephone  professes  not  only  to  convey 
intelligible  signals  to  great  distanries  without  the  use  of  a  bat- 
lerv,  V)ut  to  transmit  in  fae-siniil(!  the  tones  of  the  liuman  voice, 
so  that  a  voice  shall  be  as  certainly  recogni/.ed  when  heard  over 
a  distance  of  a  few  hundreds  of  miles  as  if  its  owner  were  speak- 
ing in  the  room  by  our  side.  And  the  telephone  does  not,  fall 
short  of  its  profession.  Scientific  men  have  had  their  wonder 
and  curiosity  aroused  even  more  than  the  unscientific  j)ublie, 
since  a  scientific  man  appreciates  the  enormous  difiTiculties  to  be 
overcome  before  .such  an  instrument  can  be  realized  Had  any 
hardy  speculator  a  few  years  ago  proposed  a  telephone  which 
shotdd  act  on  the  principle,  and  be  con.structed  in  the  form,  of 
Mr.  Bells  instrument,  lie  would  probably  have  been  considered 
a  lunatie.3  Theeil'ects  are  so  marvellous;  the  exciting  causes  at 
first  sight  so  entirely  inadequate  to  produce  them.  For  a  tcle- 
j)honie  message  diil'ers  as  widely  from  an  onbnary  telegraphic 
mes.sage  as  a  highly  finished  oil  painting  diilers  from  a  i^age  of 
print.  In  the  one  you  have  only  white  and  black — black  sym- 
bols on  a  white  ground — the  .symbols  being  limited  in  number, 
and  recurring  again  and  again  \:ix\\  wero  dilTercnces  of  order. 
Tht;  painting,  on  the  f)ther  hand,  discloses  eveiy  variety  of  color 
and  arrangement.  No  sh-.rp  lines  of  discontinuity  oiTend  the 
eye:  f)n  the  contrary,  the  tints  shade  oil;  gradually  and  softly 


'  Krciiii  the    \['(,i/mhi.iter  liecitii: 


a  Sue  IJiiill 


f  s  iiri-dictioii,  lKif,'u  17 


.a^ 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


// 


</ 


#. 


1.0 


I  I.I 

11.25 


Ij^  12.8 

|50     ""■ 


|Z5 


1.8 


1.4    ill  1.6 


V] 


<^ 


/2 


^;; 


/A 


IE.  vu 


•     • 


Sciences 
Corporation 


33  WfcST  MAIN  STREET 

WEBSTER,  NY.  14580 

(716)  872-4503 


^ 


84 


THE   SPKAKING  TELEPHONE. 


into  each  other,  presenting  tone  and  depth  in  endless  variety. 
The  page  of  print  is  iinintelhgible  without  tlic  aid  of  a  key;  tiie 
painting  tells  its  story  plainly  enough  to  any  ono  who  has  eyes 

to  SCO. 

Let  us  inquire  for  a  moment  what  is  the  nature  of  the  appar- 
atus which  wo  have  been  using  for  tiie  last  thirty  or  foi'ty  yeai"s 
for  the  transmission  of  telegraphic  signals.  The  instruments 
chiefly  employed  have  been  the  single  needle  telegraph  and  the 
Morse  instrument.  In  tlio  former  a  coil  of  wire  surrounds  a 
magnetized  needle,  which  is  suspended  in  a  vertical  position. 
When  an  electrical  current  passes  through  the  coil,  the  needle  is 
deflected  to  i-ight  or  left,  according  to  the  direction  of  the  cur- 
rent. The  .sender,  by  means  of  a  handle,  can  pass  cither  positive 
or  negative  currents  into  the  circuit.  The  right  and  left  deflec- 
tions of  the  needle  are  combined  in  varitms  ways  to  form  the 
lettei-s  of  the  alphabet,  and  the  lettera  form  words.  Thu.s,  at 
the  sc'uling  station  a  message  is  broken  up  into  little  bits,  each 
bit  or  part  of  a  bit  transmitted  separately,  and  the  process  of 
building  these  up  again  performed  at  the  iv<'eiving  station. 
Some  of  the  lettei-s  of  the  aliihabet  are  indicated  by  a  single 
movement  of  the  needle,  that  is,  by  a  single  ciu'rent ;  for  othere, 
as  many  as  four  are  required. 

In  the  !^^()rse  instrument  only  one  current  is  utilized,  which 
may  be  either  positive  or  negative,  and  the  requisite  variety 
is  obtained  by  allowing  the  current  to  })ass  through  the  cir- 
cuit for  a  longer  or  shoii:(>r  interval.  The  essential  ])art 
of  the  instrument  consists  of  an  electro-magnet  with  an  iron 
armature  attacheil  to  one  end  of  a  lever.  At  the  otluM'  end 
of  the  lever  is  a  pointer  or  pencil,  and  a  paper  ribbon  moves  at 
a  constant  rate  in  front  of  the  end  of  the  pointer.  When  the 
coils  ol  the  elcctro-niagnct  arc  traversed  by  a  current,  the  iron 
armatui'c  is  attracted,  and  the  pointer  comes  in  contact  with  the 
paper  ribbon,  on  which  it  makes  a  mark,  long  or  short,  according 
to  the  duration  of  the  cui  ront  Thus  are  produced  the  dots  and 
dashes.  These  arc  combined  in  a  similar  way  to  the  right  and 
left  movements  of  the  needle  in  the  needle  iustruracut     In  some 


UNDri.ATIXr.   CI'IUIKXTS. 


85 


H  :i 


of  tlio  more  reiinccl  instruments  letters  arc  indicated  and  even 
printed  directly  at  the  receiving  station.  Tlii.s  is.  of  course,  a 
great  simplilication  ;  but  with  such  arrangcniciits  we  cannot  liuve 
more  tliaii  tliis.  The  page  of  print  rei)resents  the  limit  of  wiiat 
such  instrimicnts  and  methods  can  do  for  us.  It  is  true  that  a 
skilled  operator  with  the  Morse  instrument  can  interpret  the  sig- 
nals as  they  arrive  without  looking  at  the  murks  on  the  paper, 
simply  by  using  his  ears.  i<]vcry  time  the  circuit  is  made  or 
broken  a  click  is  heard,  and  long  practice  has  taught  him  to  i-ely 
on  the  evidence  of  his  ears  with  as  much  confidence  as  one  less 
accustomed  to  the  work  would  trust  his  eyes.  Nevertheless,  he 
hears  only  a  succession  f)f  clicks,  which  must  Ijc  interpreted 
before  th(y  becom(»  intelligible  to  any  one  but  himself. 

In  these  forms  of  apparatus,  it  will  be  observed,  the  eiirrents 
are  intermittent;  each  current,  circulating  through  the  coil,  is 
followed  by  an  interval  of  rest.  Tluy  begin  and  eml  ;ibru!itly, 
and  all  perform  the  same  kind  of  work;  that  i.s,  they  (h'llect  a 
needle,  or  produce  mai'ks  on  a  jiiecc  of  paper.  Telc})honic  cur- 
rc'its.  on  the  other  hand,  rise  and  fall,  ebb  and  ilow.  chang(>  in 
intensity  within  comparatively  wide  limits,  but  pi'cserve  their 
continuity  so  long  as  "(Uitinuous  sounds  arc  being  uttered  in  the 
neighborhood  of  the  telephone.  Tiny  ari'  called  nndulatory 
current.s,  to  distinguish  them  from  the  intermittent  currents  of 
tlic  ordinary  telegraphic  apparatus  ;  and  their  peculiar  character 
is  an  essential  feature  of  the  telephone. 

No  skill  or  training  is  required  for  the  efl'ectivo  use  of  the 
telephone.  The  operator  has  merely  to  press  the  instrumcit  to 
his  ear  to  hear  distinctly  every  .sound  transmitted  from  the  dis- 
tant end.  For  this,  it  is  true,  an  eflort  of  attention  is  rc(juired, 
and  some  persons  use  the  insti'ument  at  the  tirst  trial  with  more 
.success  than  othcns.  Individuals  diifer  in  the  facility  with  which 
they  ure  able  to  concentrate  their  attention  on  one  car,  so  as  to 
be  practically  insensible  to  what  goes  on  around  them.  But  this 
habit  of  attention  is  readily  acquired,  and  when  it  is  once 
accpiired  tJie  telephone  may  l)e  used  by  any  one  who  has  (\ai's 
to  hear  and  a  tongue  to  spe;''  .     In  sending  a  message,  the  iustru- 


86 


TIIK  .Sl'KAKlNci  TKI-KIMIONE. 


ment  is  held  aVtoiit  i\n  iiicli  in  front  of  the  mouth,  and  the  sender 
merely  tiUlvs  into  the  inoutlipiecc  in  his  ordinary,  natural  man- 
ner. The  words  are  repeated  by  tlie  instrument  at  the  other  end 
of  the  circuit  with  the  same  pitch,  the  same  cadences,  and  the 
same  relative  loudness.  But  what  strikes  otio  the  most  is  that 
the  character  of  the  speaker's  voice  is  faithfully  preserved  and 
reproduced.  Thus  one  voice  is  readily  distinguished  from 
another.  No  peculiarity  of  inflection  is  lost  Nor  is  this 
result  effected  over  short  distjuices  only.  No  doubt  a  sen- 
tence will  be  heard  with  diminishing  distinctness  as  it  comes 
over  an  increasing  distance.  In  this  country  cxjieriments  have 
not  yet  been  made,  so  far  as  we  know,  over  very  long  dis- 
tances; but  Mr.  Bell  states  that  he  carried  on  a  conversation 
without  any  difficulty  between  Bo.'ston  and  Now  York,  two  hun- 
dred and  fifty-eight  miles  apart,  through  an  ordinary  telegraph 
wire.  A  man's  breathing  was  distinctly  heard  one  hundred  and 
fortv-nine  miles  away.  At  the  Newport  torpedo  station,  in 
Rliode  Island,  speaking  was  carried  on  through  a  line  including 
five  miles  of  submerged  cable  and  an  equal  length  of  land  wire. 
Resistance  coils  were  added  two  thousand  ohms  at  a  time,  until 
twelve  thousand  ohms  were  introduced  into  the  circuit,  without 
interfering  with  the  transmission  of  speech.  Tlie  importance  of 
this  test  will  be  understood  when  it  is  remembered  that  the  ve- 
sistimce  of  the  Atlantic  cable  is  e(pial  to  seven  thousand  ohms 
only.  1  The  experiments  at  Newport  were  continued  by  the  addi- 
tion of  a  total  resistance  of  thirty  thousand  ohms,  but  beyond 
twelve  thou.sand  ohms,  tlie  sound  was  found  to  diminish  in  inten- 
sity. Mr.  Bell  states  that  the  maximum  amount  of  resistance 
through  which  the  undulating  current  will  pass,  and  yet  retain 
sufficient  force  to  produce  an  audible  sound  at  the  distant  end. 


1  It  by  no  meiinH  follows,  as  the  writer  would  lend  us  to  infer,  that  the  tclopUono 
ciui  be  used  tn  triiiisinit  artiouliite  s|iui'oh  throii^fh  i:xti'iide<l  l>;ni;ths  of  eahlo  simply 
beoauso  it  has  s.rved  well,  under  very  dissimilar  eireiimstuiices,  to  eomiriunieate 
throu);h  un  etiuivalent  resistaneo  of  artifleiul  line.  The  hnvs  retrardinj^  tlie  phenom- 
enon of  induetive  retardation  in  lonjf  oeean  eables.  like  those  aeross  tlie  Atlantic, 
liold  (food  for  eurrerts  produeed  by  the  teleiihone  as  well  as  for  currents  derived 
from  any  other  source  whatever. 


IXDfCTlOX   (TRRKNTS. 


87 


has  yet  to  be  determined.  In  the  laboratory  he  has  conversed 
through  a  rosistanco  of  sixty  thousand  ohms.  Tliere  is  a  prac- 
tical diiliculty  in  traiismitting  telephonic  signals  through  a  tele- 
graph wire  running  parallel  to  a  number  of  other  wires  which 
are  being  used  for  ordinary  telegraphic  purposes.  Induction 
currents  are  produced  in  the  telephone  wire,  whi(fh  greatly  inter- 
fere with  the  distinctness  of  the  sounds.  The  difliculty  is  said 
to  be  overcome  by  having  an  e.xtra  return  wire,  instead  of  util- 
izing the  earth  for  a  part  of  the  (tircuit,  as  is  ordinarily  done. 
The  two  wires  are  put  side  by  side  in  close  proximity,  ami  the 
detrimental  cllcct  of  tlie  inductive  currents  is  thus  partially  or 
entirely  disposed  of.  The  following  extract  from  a  letter  which 
appeared  in  the  Daily  News  a  few  weeks  ago  shows  that  induc- 
tive action,  when  the  parallel  circuits  are  not  numerous,  does  not 
seriously  interfere  with  the  transmlssi(jn  of  speech: 

The  experiments  with  the  telephone  were  made  by  mo  upon 
the  cable  lying  between  Dover  and  Calais,  which  is  twenty-one 
and  three-ipiarter  miles  long.  Several  gentlemen  and  ladies 
were  present,  and  conversed  in  French  and  English  with  a  second 
party  in  France  for  upwards  of  two  hours.  There  was  not  the 
slightest  failure  during  the  whole  tune.  I  was  only  using  one 
wire.  The  other  three  (it  is  a  four  wire  cable)  were  working  di- 
rect with  London  and  I'aris,  Calais  and  Lille.  I  could  distinctly 
hear  the  signals  by  the  three  wires  on  the  telephone,  and  at 
times,  when  but  one  of  the  three  wires  was  working,  1  could 
decipher  the  Morse  signals,  and  read  a  message  that  was  passing 
from  Glasgow  to  Pans.  Yet  when  all  the  tliree  wires  were 
working  simultaneously,  the  telephone  sounds  were  easily  and 
clearly  distinguishable  above  the  click  of  the  signals .  I  hap- 
pened to  know  several  of  the  ])arty  in  France,  and  was  able  to 
recognize  their  voiee.>*.  They  also  recognized  mine,  and  told  us 
immediately  a  lady  spoke  that  it  was  a  female  voice.  When 
making  some  trials  upon  a  line  three  fourths  of  a  mile  long,  I 
arranged  a  musical  box  (the  tones  of  wliich  are  very  feeble)  un- 
der the  receiver  of  an  air-pump,  the  top  of  the  receiver  being 
open.     Upon  this  opening  I  placed  the  telephone,  and  every 


88 


THE   SPEAKTXrr  TELEPHONE. 


note  came  out  at  tlio  second  en  J  so  clearly  as  to  enable  those  who 
were  present  to  name  the  tune  that  was  played.  Unfortunately 
we  liad  not  the  same  means  in  Knvnce,  but  simply  iield  the 
jnouth  of  the  telephone  close  to  tlie  box,  and  some  of  the  notes 
were  audible,  but  not  so  perfect  as  on  the  short  line.  One  younf^ 
lady  burst  out  laughing  tlie  moment  she  placed  the  instrument 
to  her  ear,  and  exclaime!,  ''Si /me  one  is  whistling,  'Tommy, 
make  way  for  your  uncle!'"  As  my  correspcmdont  and  my.self 
liad  had  a  little  practice,  we  were,  without  the  slighte.st  difliculty, 
able  to  talk  in  our  usual  manner,  without  any  strain  upon  the 
voice  or  any  uimatural  lengthening  of  .syllables.  We  were  not 
able  to  hear  bre.-ithlng,  in  conseipicnce  of  the  continued  ])ecking 
caused  bv  indnetion  from  otiier  wires. 

The  construction  of  the  telephone  (tig.  57)  is  remarkably  simple. 


Fig.  57. 

It  consists  of  a  steel  cylindrical  magnet,  about  five  inches  long 
and  three  eighths  of  an  inch  in  diameter,  encircled  at  one  ex- 
tremity by  a  short  bobbin  of  wood  or  ebonite,  on  whicii  is  wtjund  a 
quantity  of  very  fine  insulated  copper  wire.  Tlie  magnet  and 
coil  are  cont;iined  in  a  wooden  cylindrical  ca.sc.  The  two  ends 
of  the  coil  are  soldered  to  thicker  ])ieces  of  copper  wire,  which 
traverse  the  wooden  env(^lo]ie  from  one  end  to  the  other,  and 
terminate  in  the  binding  sei'cws  at  its  extremity.  Inunediately 
in  front  of  the  magnet  is  ;i  thin  circular  u'on  plate,  wiiich  is  kept 
in  its  place  by  being  jiunmed  between  the  main  portion  of  the 
wooden  ease,  and  a  wooden  cap  carrying  the  mouth  or  ear 
trumpet.  Tlieso  two  jiarts  are  screwed  together.  The  latter  is 
cut  away  at  the  centre,  so  as  to  expose  a  portion  of  the  iron  plate, 


TlllCKNKSii   UK  'I'llK   DIAI'IIHAOM. 


89 


iib)Ut  half  iin  iiicli  in  diameter.  In  the  experiments  which  Mr. 
Bell  lias  carried  out  in  order  to  determine  the  influence  of  the  vari- 
ous piirts  of  the  teleplionc  on  flic  results  j^rodnced,  and  their  rela- 
tions to  each  othorwhen  the  best  elfeets  ar(!ol)tained,  he  ciiijiloyed 
iron  jihites  of  various  areas  and  tiiicknesses,  from  hoiler  plate 
tliree-eighths  f  an  inch  in  tliiekncss  to  the  thiimest  ]ilate  pro- 
<'urable.  Wonderful  to  relate,  it  ajipears  that  scarcely  any  plate 
is  too  thin  or  too  thick  for  the  purpose,  hut  the  hest  thickness  is 
that  of  the  ferrotype  plate  used  by  jihotograjihers.  Thin  tin 
plate  also  answers  very  well.  The  iron  plate  is  cut  into  the  form 
of  a  disk,  ahont  two  inches  in  iliauieter,  and  is  placed  as  near  as 
possilile  to  the  extremity  of  the  steel  magnet  witiiout  actually 
toucliing  it;  the  cfleet  of  this  position  lu'ing  that,  while  the  in- 
duced nuignctism  of  the  plate  is  considerahlc,  it  is  .susceptible  to 
very  r,\\ui\  eliMUges.  owing  to  tlus  freciloin  with  which  the  plate 
can  vibrate.  The  dimensions  of  the  various  parts  oC  the  instru- 
ment her(!  given  are  found  to  lu;  convenient,  but  they  are  by 
no  uiciiiis  essential.  Good  results  have  been  obtaiiuMl  by  means 
of  a  magnet  only  an  inch  iind  a  half  long,  and  a  working  instru- 
ment need  not  be  to(j  large  foi"  the  waistcoat  jjocket.  There  is  no 
dillerencc  between  the  transmitting  and  the  receiving  tele|ilione; 
each  instrument  serves  both  ])urposes.  Nevertheless,  in  order  to 
avoid  the  ineonvenience  of  shifting  tin;  instrument  backwards 
;••.({  forwards  bet'-  en  the  ear  and  iIk^  n.'outli.  it  is  better  to  have 
two  on  the  circuit  at  each  .station.  The  operator  then  holds  one 
|icnnanently  to  his  ear,  while  he  talks  with  the  other. 

it  will  not  be  suppos(>d  that  tlic^  idea  of  this  marvellously 
.simjile  piece  ot  .-qjparatus  w;is  cvolveil  ready  formed  from  the 
inventors  brain:  veiy  far  otherwise.  It  is  the  final  outcome  of  a 
long  series  ot  ]);itient  researches  c;irried  out  by  ^[r.  Bell  in  the 


most  SKI 


ful 


and 


nnUoson 


hieal 


manner,  in  which  one  modilica 


tion  suirifested  another,  accessorv  a 


fter 


accessorv  was  Hiscardci 


and  linallv  the  instrument  was  i)runed  d 


and  dunensions. 


Teh 


iMHiones 


b 


own  to  its  ]ircs(Mit  form 


iv(^  i)een  lonji  Known. 


Af 


ew 


rebv  articulate  sounds  could 


years  ago  a  simple  arrangement  wher 

l)e  transmitted  over  a  distance  of  liftv  or  sixtv  vards,  oi'  e\en  fur- 


90 


rilK   SI'KAKINU   TKLKPUONK 


tlicr,  could  !)(•  l)i>ii!i-lit  ill  tin-  .streets  for  ii  penny.  It  consisted  of 
ii  piiii'  ol"  pill  l)o.\es,  tiie  bottoms  of  wlii(!li  were  connected  by  a 
piece  of  string  stretclied  tight,  wliihi  over  tlus  mouth  of  each  was 
))astod  tissnt^  ])aper.  On  speaking  to  mw  of  tiie  jiill  boxes  the 
tissue  ])aper  and  I'Ueloseil  air  were  set  in  vibration.  'Die  vibra- 
tions so  ])roduccd  were  eonnnunicated  to  tlie  thread  and  tnms- 
mittcd  to  the  distant  ])ill  box,  wliieli  wa-  held  cK)se  to  tlie  ear, 
where  they  affected  the  air  in  such  a  way  as  to  reproduce  the 
original  sounds.  Tlie  sim])le  apj)aratus  was  more  effective  than 
would  be  at  first  imagined.  Electric  telephones  were  devised  in 
this  country  about  the  same  time  that  the  telegraph  was  intro- 
duced, but  the  best  of  them  d'ffered  widely  from  the  modern  in- 
strument. They  were  (•apal)le  of  eoiiveving  to  a  di.stance  sounds 
of  various  pitch,  so  that  the  succession  of  notes  constituting  a 
melody  could  be  reproduced  many  miles  away,  but  the  special 
character  of  thi'  voice  by  which  the  melody  was  oi'iginated  was 
entirely  lost. ^  Now  tli(>  great  interest  which  attaches  to  Mr. 
Bell's  telephone,  and  the  intense  wonder  and  curiosity  it  has 
aroused,  are  due  to  its  ])OW(>r  of  conveying  aV).solutely  unaltered 
every  peculiarity  of  voice  or  musical  instrument,  A  violin  note 
rea{>])ears  as  ii  violin  note :  it  cannot  be  mistaken  for  anything 
else.  And  in  the  case  of  a  human  voice,  it  is  not  less  easy  to 
distinguish  one  speakei-  from  another  than  it  would  bo  if  the 
speakers  were  in  the  room  close  liy  instcail  of  being  miles  or 
even  hundreds  of  miles  away.  'IMiis  is  the  charm  of  the  new 
telephone;  this  it,  is  which  renders  it  immeasurably  superior  to 
anything  of  the  kind  which  prt'ceded  it. 

Mr.  Bell's  researches  in  el(!Ctrio  telephony  began  with  the  arti 
licia!  proiluetion  of  musical  sounds,  suggested  by  the  work  in 
which  he  was  then  engaged  in  Boston,  viz:  teaching  the  deaf 
and  duml)  to  speak.  Deaf  mutes  are  dumb  merely  because 
they  are  deaf.  There  is  no  local  defect  to  prevent  utterance, 
and  Mr.  Bell   has  jjractically  demon.strated  by  two  tlum.sand  of 


'  Rc'ihs'k  teli-'plione  was  tlio  first  inveiitioti  which  could  lu'oompli.sli  tlio  ri'siilt 
here  Htated.  ami  this  was  mvcnti'il  in  (funimiiy,  in  tHiil.  Scu  (Ifsuripticm  of  Kuiss's 
tclephoui',  \>ui!v  II. 


TKACINGS   OK   AlK   VIUllATIONS, 


91 


his  own  pujiils  Unit  wli 'ii  tlio  deut'  and  dumb  know  liow  to  con- 
trol tlio  iictioii  ()[  tlioir  vocid  organs,  they  van  urticiiihito  witli 
conipiinitivo  fticility.  Striving  to  perfect  his  system  of  teaching, 
it  oeetirred  to  Mr.  Bell  that  if,  instead  of  presenting  to  tiie  eye 
of  tiie  deaf  mute  u  system  of  symbols,  lie  couhl  make  visible 
the  vibrations  of  the  air,  the  apparatus  might  l)o  used  as  a  means 
of  teaching  articulation.  In  tliis  ]iart  of  his  investigations  Mr. 
Bell  derived  great  assistance  from  the  phouaulograpli.  He  suc- 
ceeded in  vibrating  by  the  voice  a  style  of  wood,  about  a  foot  in 
length,  attached  to  tiie  mend)rane  of  the  phonautograph ;  and 
with  tills  he  obtained  enlarged  tracings  of  the  vibrations  of  the 
air,  ])roduced  by  tlie  vowel  sounds,  upon  a  i)lane  surface  of 
smoked  glass.  Mr.  Bell  traced  a  similarity  between  the  manner 
in  which  this  piece  of  wood  was  vibrated  by  the  membrane 
of  the  iihonautograph  and  the  manner  in  which  the  ossiculte 
of  the  human  ear  were  moved  by  the  tympanic  membrane. 
Wishing  to  construct  an  apparatus  closely  reseml)ling  tlie 
liuman  ear,  it  was  suggested  to  him  by  Dr.  Clarence  J. 
Blake,  a  distinguished  aurist  of  Boston,  that  the  human  ear 
itself  would  l)e  still  better,  and  a  specimen  was  prcjiared.  Our 
readers  are  aware  that  the  tympanic  membrane  of  the  oar  is  con- 
nected with  the  internal  ear  by  a  series  (jf  little  bones  called  res 
pectively  the  malleus,  the  incus  and  the  stapes,  front  their  [)ecu- 
liarsiiapes.  and  that  by  their  means  the  vibrations  of  the  tympanic 
membrane  are  communicated  to  the  internal  ear  and  the  audi- 
tory nerves.  Mr.  Bell  removed  the  stapes  and  attached  to  the 
end  of  the  incus  a  style  of  hay  about  an  inch  in  length.  L'pon 
singing  into  the  external  artilicial  ear,  the  style  of  hay  was  thi'owii 
into  vibration,  and  tracings  were  obtained  upon  a  ])lane  surface 
of  smokeil  glass  passed  rapidly  underneath.  The  curves  so  ob- 
tiiined  are  of  great  interest,  each  showing  peculiarities  of  its  own 
dependent  upon  the  vowel  sound  that  is  sung.  Whilst  engaged 
in  these  experiments  Mr.  Bell's  attention  was  arrested  by  obi-erv- 
ing  the  wonderful  dispi-oportion  which  exists  between  the  size 
and  weight  of  the  membrane — no  thicker  than  tissue  paper — 
and  the  weight  of  the  bones  vibrated  by  it,  and  he  was  led  to 


92 


TIIK   UPKAKING  TKUKl'HONE. 


inquire  wlictlicr  a  tliiuker  iiu^ml)riui('  iniglit  not  he  iiblf  to  vibrali- 
ii  piece  of  iron  in  front  of  an  clectro-iMagiu't.  TIk^  exjieriiuent 
was  at  once  tried.  A  piece  of  steel  spring  was  attached  to  a 
stretched  membrane  of  gold  beater's  skin  and  })laeed  in  front  of 
the  pole  of  th»^  magnet  Tiiis  answered  very  well,  but  it  was 
found  that  the  action  of  the  instrument  was  improvi'(l  by  in 
creasing  the  area  of  nietid,  and  thus  the  menil)rane  was  done 
away  with  and  an  iron  ])lat(>  substitute(l  for  it.  It  was  important 
at  the  same  time  to  determine  tlmelTeet  produced  by  altering  the 
strength  of  the  magnet;  that  is,  of  the  current  which  ]iassed 
round  the  coils.  The  battery  was  graduall}' rcibiccd  from  lifty 
cells  to  none  at  all.  and  '<till  the  etl'ects  were  observeil,  i)Ut  in  a 
less  niarke(l  degree.  The  action  was  in  this  hitter  ca.se  doulitless 
due  to  residual  magnetism:  hence,  in  the  present  fonu  of  appai'- 
atus  a  permanent  magnet  is  employed.  Lastly,  the  eiTect  of 
varying  the  dimensions  of  the  coil  was  stU(li(Ml.  when  it  was 
found  tiiiit  the  sounds  became  louder  as  its  length  was  dimin- 
i.shed;  acerUiin  length  wa.><.  however,  ultimately  reached.  Iieyoud 
whicli  no  improvement  was  efTected,  an<l  it  was  fouixl  to  l)et)nly 
neces.sary  to  enclose  one  end  of  the  magut't  in  the  coil  of  wire. 

Such  was  the  instrument  that  Mr.  Hell  sent  to  the  Centennial 
K.\hil)ition  at  J'liiladel))hia.  The  following  is  the  ollicial  report 
of  it,  signed  by  Sir  William  Thomson  and  others  : 

Mr.  Alexander  Graham  Jiell  exhil)its  an  apparatus  by  which 
he  has  achieved  a  result  of  transcendent  scientilic  interest — a  trans- 
mis.sion  of  spoken  words  by  electric  currents  through  a  telegraph 
wire.  To  obtain  this  result  Mr.  Bell  ])erceived  that  he  must  ])ro- 
duce  a  variation  of  strength  of  current  as  nearly  as  may  l)e  in 
exact  ])roj)ortion  to  the  velocity  of  a  particle  of  air  moved  by  the 
.sound,  and  he  invented  a  method  of  doing  so — a  jiiece  of  iron 
atUiched  to  a  mem])rane  (tig.  08).  and  thus  moved  lo  and  fro  in 
the  neighborhood  (<f  au  electro-magnet,  whicii  has  jjroved  per- 
fectly successful.  The  battery  and  wire  of  this  electro-magnet  are 
in  circuit  with  the  telegraph  wire  and  the  wire  of  another  electro- 
magnet at  the  receiving  station.  This  second  electro-magnet  has 
a  solid  bar  of  iron  for  core  which  is  connected  at  one  end  by  a 


silt    WIM.IAM     I  lloMSO.V  S    KKI'dlCT. 


98 


thick  disk  of  inm  to  an  iron  lulu'  .siutouikIIii^'-  ''  ..;l  and  i)ai'. 
'I'lio  frcd  circular  i-ntl  of  tho  tul)e  constitutes  oii"  jiojo  of  tlie 
t'lectro-nui^'uct,  and  tlio  adjacent  free  end  of  tlic  Itar  core  tiie 
other.  A  tliin  circular  iron  disk',  lield  jircssccl  iiLTainst  tlioendof 
the  tul)c  hy  tho  clectro-nia^'nctic  uttractiou  and  free  to  vil)rato 
throujrh  a  very  HUiall  space  without  toncliinjf  the  central  ])ole, 
conatitutea  tho  sounder  i)y  whicli  the  electric  eli'ect  is  reconverted 


Pig.  58. 


into  sound  (liL'.  oOY  With  iny  ear  pressed  apainst  this  disk,  I 
iicard  it  speak  distinctly  several  .sentences.  1  necil  scarcely  say 
1  was  astonished  and<lelighted.  So  were  others,  including  .some 
judges  of  our  group,  who  witnes.sed  tlio  experiments  and  verilied 
with  their  own  ears  the  electric  traiisinission  of  s])('ech.  This, 
perhapd,  the  greatest  marvel  liithcrto  achieved  by  tho  electric 


Fiij.  '.9. 

lelegraph,  has  been  obtained  by  appliances  of  quite  a  homespun 
and  rudimentary  cliaracter.  With  somewhat  more  adxanced 
plans  and  more  powerful  api)aratus,  we  may  contidently  ex- 
pect tliat  Mr.  Bell  will  give  us  the  means  of  making  the  voice 
and  spoken  words  audible  through  the  electric  wire  to  an  ear 
hundreds  of  miles  distant 

The  present  form  of  instrument,  which  is  now  being  manu- 


94 


TIIK   SI'KAKINn      KLKIMIOXE. 


facturt'd  in  'aiyi^  iiuiiil)ors  liy  tlic  Silvertowu  Coiiijiuny,  ilncs  iinl 
cssciitiiill V  ililTei'  IViim  tlml  rcpDrtc^d  on  so  I'ntliiisiiistically  !•}' 
Sir  W'illiiiiii  'I'liomsoii.  Only  it  is  iiioih;  siiii|pl('  in  construction 
and  more  luiiidy. 

,  Hcl'orc.  iittmiptinjr  any  cxjilanation  of  tlio  action  of  the  tele- 
j)lioiic,  it  may  lu;  well  to  draw  tlio  attention  of  oiir  readers  to  tlic 
special  cliaracteristics  of  the  human  voi(!C.  ami  to  tiiose  j)ecuiiari- 
ties  wlp'h  distintniisli  one  musical  note  from  another.  What- 
ever u  e  dill'ereiices  in  (juestion  may  depeml  upon,  it  is  certain 
tliat  tliev  ire  transmitted  and  repro<lueed  iu  tii<!  tele|)iione  witli 
unerring  lidelitv,  and  it  is,  therefore,  important  tiiat  \vu  whoidd 
imderstand  tiieir  nature  and  orij.'in.  Tal<e  a  tuniu;;-  fork  an<l  set 
it  in  vil>iatiou  liy  strikinj^  or  drawing  a  violoncello  how  ai'i'oss 
its  ])roujrs.  The  fork  yields  its  own  proper  jiotu,  which  will  be 
loud  or  the  reverse,  accordin<r  as  the  fork  has  been  struck  ener- 
getically or  lightly.  So  long  as  wo  u.so  one  fork  oidy  it  isol)vious 
that  th(^  only  variation  which  eau  be  ])rodueed  in  tho  sound  is  a 
variation  of  intensity,  if  tho  extent  of  vibration  bo  snudl,  the 
resulting  .souml  is  feeble;  its  lomlness  increases  with  thoe.xeur 
sioii  of  the  prongs.  What  is  true  of  tho  tuning  fork  is  true  of 
any  other  musical  instrument,  and  hence,  generally,  tho  ItMidne.ss 
of  a  imisical  sound  depends  uj)on  tho  amplitude  of  vibration  of 
that  which  ))roduccd  it  Now,  take  two  similar  tuning  forks  of 
dillerent  ])iteh,  anil  suuposo  that  one  is  exactly  an  octave  above 
tlic  other.  They  may  bo  e.xcitod  in  such  a  way  that  th(!  notes 
emitted  are  of  eiiual  loudness,  and  then  tho  only  res|)ei!t  in  which 
they  differ  from  each  other  is  in  jiitch.  Tho  jiiteh  of  a  fork  de- 
jK'uds  upon  its  rate  of  vibration.  It  is  comparatively  easy  with 
.«aiitable  apjiaratus  to  measure  the  rate  of  vibration  of  a,  tuning 
fork,  and  were  we  to  test  the  two  forks  in  (question,  it  would  be 
found  that  that  giving  tho  higher  ni>te  vibrates  cxactlv  twice  as 
fast  as  the  other.  If  tho  one  performs  a  hundred  oscillations  in 
ji  second,  the  other  which  is  an  octavo  above,  comj)letes  two 
hundred  in  the  same  interval  of  time.  Thus,  tho  pitch  of  a  note 
yielded  by  a  tuning  fork  <le{)etuls  upon  its  rate  of  vibration,  and 
ou  nothing  else,  and  the  same  is  true  of  a  ])iauo-forte  wire,  the 


<;iIAI!A(TKJ{ISTICS    Ol"   S(trM). 


'J5 


jiir  in  nn  orpnn  I'ipf.  n  linnrioniiiiri  rood,  otc  We  liavo  now  nc 
<M)iint'  (1  for  two  of  tlio  cliiinictoristics  of  a  iniisicul  note,  its  loiul- 
iifss  iiii'i  its  pitcii ;  but  tli>Te  isii  tiiird,  cqimlly,  if  not  iiioro  iin- 
jMirtniit,  iiiifl  t)y  no  mciiiis  so  simplf  of  cxpliiiuitioii.  W'c  rcfr-r 
to  what  is  usually  spoken  of  in  Knirlisli  books  on  acoustics  as 
the  (juality  of  the  note  ;  the  Freiieh  ciill  <'  tinil)re  and  the  (Jor- 
inaiis  klan^ffarbe.  It  is  that  which  constitates  the  dillcrcnce  be- 
tween a  violin  and  an  or^Mii,  or  between  an  or^un  and  a  |iiiino- 
forte,  or  between  two  human  voi 'cs ;  ind(.'cd  between  any  two 
musical  sounds  which  are  of  the  same  pitch  and  louchiess,  but 
are  still  distiuffuishable  from  each  other  In  order  to  explain  the 
physical  cause  of  quality,  we  will  suiiposc  we  have  ;i  thin  metallic 
wire  about  a  yard  lon<?  stretched  between  two  points  over  a 
soundin<r  I)oaril.  When  plucked  at  its  centre  the  wire  vibrates 
jis  a  whole ,  the  two  en<ls  are  points  of  rest,  and  a  loop  is  formed 
between  them.  The  note  emittc<l  by  the  wir(>  when  vibratinj^ 
in  this  manner  is  called  its  fuiulanu'iital  note.  If  the  wire  be 
damped  a^  its  centre,  by  layinj^  on  it  witii  slight  pressure  the; 
feather  of  .i  quill  pen,  and  pluck«'d  at  a  [loint  half  way  betwcvn 
the  cientre  and  one  end,  both  halves  will  vibrate  in  the  same 
manner,  and  independently  of  each  other.  That  is  to  say,  there 
will  1)G  two  eipial  vibrating  segments  and  a  point  of  rest  or  node 
nt  the  centre.  ]?ut  the  rapidity  of  vibration  of  each  segment  will 
be  twi(!e  as  great  as  tliat  of  th(!  wire  -rhen  vibrating  as  a  whole, 
and  consequently  the  note  emitted  will  be  the  octivve  of  the  fun- 
damental. When  damped  at  a  point  one  third  of  the  length  from 
either  extremity,  and  ])Iucked  half  way  between  that  point  and 
till*  nearer  extremity,  the  wire  will  vibrate  in  three  ccpial  di\  i- 
sion.s,  just  as  it  vibrates  in  two  divisions  in  the  previous  oas^e. 
The  rate  of  vibration  will  be  now  three  times  as  great  as  at 
fii-st,  and  the  note  produced  will  be  a  twelfth  abov(!  the  funda, 
mental.  Similarly,  by  damping  and  plucking  atsuitidile  ])oints 
the  wire  may  be  made  to  vibrate  in  four  jkuLs,  live;  part.s,  six 
parts,  etc.,  the  rate  of  vibration  increasing  to  four,  five,  six, 
etc.,  times  what  it  was  at  fii-st.  Let  us  suppose  that  when 
the  wire  was  swinging  as  a  whole,  and  sounding  its  fundamental 


96 


'rriK   SI'KAKINC    TKI.KI'HOXE. 


iiot(\  the  number  of  oscillations 


po 


I'l'ormed  in  a  second  was  one 


liundivd.  Then  we  sec  that  by  takinji'  suitable  j)i'eeautions  tlie 
wire  can  Ijcniade  to  break  up  into  two,  three,  I'our,  live,  six,  etc., 
vibrating  segments,  the  rates  of  vibration  l)eingres[)ectively  two 
hundred,  three  hundred,  four  hundred,  live  liunibvd,  six  liundred, 
etc.,  and  the  series  of  note.s  emitted  being  the  octave  abcjve  the 
fundamental,  the  lifth  above  the  octave,  the  double  octave,  the 
third  and  fifth  above  the  double  octave,  and  so  on.  We  now 
come  to  an  important  point,  which  is  this — that,  the  wire  l)eing 
free,  it  is  practically  imiiossible  to  .strike  or  pluck  it  in  such  a  way 
as  to  make  it  vibrate  aecoi'ding  to  one  of  the  above  systems  only. 
Jt  will  vibrate  as  a  whole  wherever  and  however  it  be  struck,  but 
this  mode  has  always  a.ssociated  with  it  or  superpo.«ed  upon  it 
.some  of  the  other  modes  of  vibration  to  which  we  have  just  re- 
feiTed.  In  other  words,  tlie  fundamental  note  is  never  heard 
alone,  but  always  in  condonation  with  a  certain  nuird)er  of  its 
overtones,  as  they  arc  called.  Each  form  of  vibration  called  into 
exi.stenee  sings,  as  it  were,  its  own  song,  v.-ithout  lieecling  what  iy 
being  done  by  its  fellows,  and  the  con.sequencc  is  that  the  sound 
which  reaches  the  ears  is  not  simple  but  highly  coni[)()sit'j  in  its 
character.  The  word  clang  has  l)een  siiggestcd  to  denote  such  a 
eomjKxsite  sound,  the  constituent  simple  sounds,  of  which  it  is  the 
aggregate,  being  called  its  1ir.st,  second,  thii'd,  etc.,  partial  tones. 
All  the  po.^sible  partial  tones  are  not  necessarily  present  m  a 
clang,  nor  of  those  which  are  present  are  the  intensities  all  the 
same.  For  instiinee,  if  the  wire  l)e  struck  at  the  (,'cntre,  that  point 
cannot  be  anode,  but  must  be  apointof  maximum  disturbance  : 
hence  all  the  even  partial  tones  an;  exchulcd  and  only  the  odd 
one.s,  the  first,  third,  fifth,  and  so  on,  are  heard. 

That  characttristic  of  a  musical  note  or  clang,  which  is  called 
its  quality,  denends  upon  the  number  and  relative  intensities  of 
the  i)artial  tones  which  go  to  form  it.  The  tone  of  a  tuning  fork 
is  approximately  simple ;  so  is  that  of  a  stop[)cd  wooden  organ 
pipe  of  large  aperture  blown  by  only  a  slight  pressure  of  wind. 
Suoh  tones  sound  sweet  and  mild,  but  also  tame  and  spiritles.s. 
lu  the  clang  of  the  violin,  on  the  other  liand,  a  large  number  of 


SOUNDS   OF  THE   IirMAN    VOICK. 


9/ 


partial  tones  arc  represented ;  lienec  tlie  vivacious  and  brilliant 
character  of  this  instrunieiit.  Tlic  sounds  ol  the  human  voice 
arc  ])roduced  by  the  vibrations  of  the  vocal  chords,  aided  by  the 
resonance  of  the  mouth.  Tiic  si/.e  and  shape  of  the  cavitv  of 
the  mouth  may  be  altered  by  opening  and  closing  the  jaws,  and 
bv  tightening  or  loosening  the  lips.  We  should  expect  that 
these  movements  would  not  bo  without  elTcct  on  the  resonance 
of  the  contained  air,  and  sucli  proves  on  experiment  to  bo  the 
fact.  Hence,  when  the  vocal  chords  have  oi-iginatcd  a  clang 
contiiining  numerous  well  developed  partial  tones,  the  mouth 
cavity,  \>y  successively  throwing  itself  into  diflerent  postures, 
can  favor  by  its  resonance  first  one  overtone  and  then  another ; 
at  one  moment  this  group  of  partial  tones,  at  another  that.  In 
this  manner  endless  varieties  of  quality  are  rendered  possible. 
Any  one  may  prove  to  himself,  by  making  the  experiment,  that 
■when  singing  on  a  given  note  he  can  only  change  from  one 
vowel  sound  to  anotiier  by  altering  the  shape  and  size  of  his 
moutli  cavity. 

Having  thus  briefly  indicated  the  physical  causes  of  the  vari- 
ous diircrences  in  musical  notes,  and  the  production  of  sounds 
by  the  organ  of  voice,  we  will  devote  a  few  moments  to  consider 
how  these  sounds  arc  propagated  through  the  air  and  reach  the 
plate  of  the  telei)hone.  When  a  disturbance  is  produced  at  any 
point  in  an  aerial  medium,  the  particles  of  which  are  initially  at 
rest,  sonorous  undulations  spread  out  from  that  point  in  all  di- 
rectiona  These  undulations  are  th  .Tect  of  the  rapid  vibratory 
motions  of  the  air  particles.  The  analogy  of  water  waves  will 
help  us  to  undcrsUmd  what  is  taking  place  tinder  these  circum- 
stances. If  a  stone  be  dropped  into  the  still  water  of  a  pond,  a 
series  of  concentric  circular  waves  is  produced,  eacii  wave  con- 
sistinff  of  a  crest  and  a  hollow.  The  waves  travel  onwards  and 
outwards  from  the  centre  of  disturbance  along  the  surface  of  the 
water,  while  the  drops  of  water  which  constitute  them  have  an 
oscillatory  motion  in  a  vertical  direction.  That  is  to  say,  fol 
lowing  any  radial  line,  the  water  particles  vibrate  in  a  direction 
at  right  angles  to  that  in  which  the  wave  is  propagated.     The 


98 


THE  SPEAKING  TELEPHONE. 


distance  between  two  successive  crests  or  two  si\ccessive  hollows 
is  called  the  length  of  the  wave ;  the  amplitude  of  vibration  is 
the  vertical  distjince  through  which  an  individual  drop  moves. 
In  a  similar  manner  sonorous  undulations  are  propagated  through 
air  by  the  oscillatory  motion  of  the  air  particles.  But  tiiere  is 
this  impoi'tant  diilerence  between  the  two  cases,  that,  in  the  lat- 
ter, the  vibrating  particles  move  in  the  same  direction  in  which 
the  sound  is  being  propagated.  Consc(iuont]y  such  waves  are 
not  distinguished  by  alternate  crests  and  hollows,  but  by  alter- 
nate condensations  and  rarefactions  of  the  air,  the  transmission 
of  which  constitutes  the  transmission  of  sound.  The  wave 
length  is  the  distance  between  two  consecutive  condensations  or 
rarefactions.  It  depends  upon  the  pitch  of  the  transmitted  sound, 
being  shorter  as  the  sound  is  more  acute,  while  the  extent  of 
vibration  of  the  air  particles  increases  with  the  loudness.  Such 
are  the  peculiarities  of  the  vibratory  motion  in  air  corresponding 
to  the  pitch  and  loudness  of  the  transmitted  sound.  But  what 
is  there  in  the  character  of  the  motion  to  account  for  diilerence 
in  quality?  A  little  consideration  will  show  that  there  is  only 
one  thing  loft  to  account  for  these,  and  that  is  the  form  of  the 
vibration.  Let  us  incntally  isolate  a  particle  of  air,  and  follow 
its  movements  as  the  sound  passes.  If  the  disturbance  is  a 
simple  one,  produced,  say,  by  the  vibration  of  a  tuning  fork,  the 
motion  of  the  air  particle  will  be  simple  also,  that  is,  it  will 
vil)rate  to  and  fro  like  the  bob  of  a  ])endulum,  coming  to  rest  at 
each  end  of  its  excursion,  and  from  these  points  increasing  in 
velocity  until  it  passes  its  neutral  point  Such,  however,  is 
clearly  not  the  only  mode  of  vibration  possible.  If  the  disturb- 
ance bo  produced  i)y  a  clang  conij)rising  a  number  of  j)artial 
tones  of  various  intensities,  all  excited  siniultiineously,  it  is  ob- 
vious that  the  air  particle  must  vibrate  in  obedience  to  every  one 
of  these.  Its  motion  will  be  the  resultant  of  all  the  motions  due 
to  the  separate  partial  tones.  We  may  imagine  it,  starting  from 
its  position  of  rest,  to  move  forward,  tlien  stop  short,  and  turn 
back  for  an  instant,  then  on  again  until  it  reaches  the  end  of  its 
excursion.     In  returning  it  may  perform  the  same  series  of  to- 


tl 


s 
a 

St 


SONOROUS   UNDULATI'^NS. 


99 


and-fro  motions  in  the  opposite  direction,  or  it  may  move  in  a 
totally  different  way.  Nevortholess,  however  complex  its  mo- 
tion may  be — and,  as  a  rule,  it  will  be  cx-jccdingly  complex — its 
periodic  character  will  be  maintained.  All  the  tremors  and  per- 
turbations in  one  wave  length  will  recur  in  all  the  other?. 

When  sonorous  undulations  impinge  u])on  the  iror  plate  of 
the  telephone,  the  latter  is  set  in  vibration.  Its  particles  move 
to  and  fro  in  some  way  or  other.  The  complexity  of  their  mo- 
tion will  depend  upon  that  of  the  air  from  which  it  was  derived 
But  for  the  sake  of  simplicity  we  will  assume  that  the  plate  has 
a  simple  pendulous  motion.  It  will  be  remembered  that  the  iron 
plate  is  placed  (juite  close  to,  liut  not  (piite  in  contact  with,  '.he 
extremity  of  the  steel  magnet  It  becomes,  tlierefore,  itsf  If  a 
magnet  by  induction  ;  and,  as  it  vibrates,  its  magnetic  powei  is 
conhtantly  changing,  being  strengthened  when  it  approaches  the 
magnetic  core,  enfeebled  as  it  recedes.  vVgain,  when  a  magnet 
moves  in  the  neighborhood  of  a  coil  of  wire,  the  ends  of  which 
are  connected  together,  an  electrical  current  is  develojied  in  the 
coil,  whose  strength  depends  ujion  the  rapidity  with  whicli,  and 
the  disUmce  through  which,  the  magnet  moves.  In  the  t(!lei)hone 
then,  as  the  plate  moves  towards  the  coil,  a  current  is  induced  in 
the  latter  which  traverses  the  whole  lengtli  of  wire  coimecting  it 
with  the  disUmt  instrument ;  the  plate  returning,  another  current 
with  reversed  sign  follows  the  iirst  The  intensity  of  these  cur- 
rents depends,  a.s  we  have  said,  on  the  rapidity  with  which  these 
movements  are  effected,  but  is  largely  influenced  also  by  the 
fact  that  the  plate  does  not  retain  a  con.stant  magnetic  strength 
throughout  its  excursions.  Under  the  a.'^sumption  we  have  made 
with  respect  to  the  simplicity  of  the  plate's  motion,  it  follows 
that  the  induced  currents,  alternately  positive  and  negative,  fol- 
low each  other  in  a  uniform  manner,  and  with  a  rapidity  corre- 
si)onding  to  the  pitch  of  the  exciting  note.  These  currents  pass 
along  the  circuit,  and  circulate  round  the  coil  of  the  distant  tele- 
phono.  There  they  modify  the  magnetic  relations  between  the 
steel  magnetic  core  and  the  iron  j)late  in  such  a  way  that  one 
current — say  the  positive — attracts  the  plate,  while  the  other 


100 


THE   Sl'EAKIXG  TELEPHONE. 


— the  negative — repels  it  And  since  the  arriving  currents  fol- 
low each  other,  first  positive  and  then  negative,  with  perfect 
regularity,  the  plate  will  also  vibrate  in  a  uniform  iiianiier,  ;ind 
will  ])orl'onn  the  same  number  of  vil)nitions  per  second  as  did 
the  plate  of  the  sending  instrument  Hence  the  sound  heard 
will  be  an  exact  copy,  except  as  to  loudness,  of  that  produced  at 
the  sendmg  stiition.  Having  thus  followed  the  sequence  of 
phenomena  in  tliis  simple  case,  we  are  enabled  to  extend  our 
explanation  to  the  case  in  which  composite  sounds  of  more  or 
less  comjilexity — vowel  sounds  and  speech — are  transmitted. 
We  are  compelled  to  admit  that  every  detail  in  the  motion  of  an 
air  particle,  every  turn  and  twist,  nuist  be  passed  on  unaltered  to 
the  iron  mend)rane,  and  that  every  modilication  of  tlie  motion  of 
the  membrane  must  have  its  counterpart  in  a  mochtication  of  the 
induced  currents.  These,  in  their  turn,  alfecting  the  iron  plate 
of  the  receiving  telcj)hone,  it  follows  that  the  plates  of  the  two 
telephones  must  be  vibrating  in  an  absolutely  identical  manner. 
We  can  thus  follow  in  a  general  manner  the  coui-se  of  the 
phenomena,  and  explain  how  air  vibrations  are  connected  with 
the  vibrations  of  a  magnetic  plate — how  these  latter  give  rise  to 
electrical  currents,  which,  passing  over  a  circuit  of  hundreds  of 
miles,  cause  another  magnetic  plate  to  vibrate,  every  tremor  in 
the  first  being  reproduced  in  fae-simile  in  the  second,  and  thus 
excite  sonorous  undulations  which  juiss  on  to  the  ear.  We  can 
understand  all  this  in  a  general  way,  but  we  are  not  the  less  lost 
in  wonder  that  the  sequence  of  events  should  be  what  it  is. 
That  a  succession  of  currents  could  be  transmitted  along  a  tele- 
graph wire  without  the  aid  of  a  battery,  that,  by  simply  talking 
1o  a  magnetic  membrane  in  front  of  a  coil  of  wire,  the  relations 
of  the  magnetic  field  between  the  two  could  be  so  far  modified 
as  to  produce  in  the  coil  a  succession  of  electrical  currents  of 
sufficient  power  to  traverse  a  long  circuit,  and  to  reproduce  a 
series  of  phenomena  identical  with  those  by  which  the  currents 
were  brought  into  existence,  would  ha,ve  been  a  few  yeara  ago 
pronounced  an  impossibility.  A  man  would  have  been  derided 
who  proposed  an  instrument  constructed  on  such  principles. 


UNiVE^lSITY  OF 


VICTOftl>.> 
Victort*,    8    C. 


NIOLES    TUBULAll  El-ECTRO- MAGNET. 


101 


Nevertheless,  here  it  is  realized  in  our  hands.  We  can  no  longer 
doubt,  we  can  only  wonder,  and  admire  the  sagacity  and  pa- 
tience with  which  Mr.  Bell  has  worked  out  his  problem  to  a  suc- 
cessful issue. 

1  The  articulating  telephone  of  Mr.  Graham  Bell,  like  those  of 
Reiss  and  Gray,  consists  of  two  parts,  a  transmitting  instrument 


Fig.  60. 

and  a  receiver,  and  one  cannot  but  be  struck  at  the  extreme 
simplicity  of  both  in.struments;  so  sin)]ile,  indv  .',  that  were  it 
not  for  the  high  authority  of  Sir  William  Thomson,  one  might 
be  pardoned  at  entertaining  some  (h)ubts  of  their  capability  of 
producing  such  marvellous  results. 

The  trausmittiug  instrument,  which  is  represented  in  fig.  60, 


Fiij  01 

consists  of  a  horizontal  elcctro-maiiiiet,  nttachcd  to  a  pillar  about 
2  inches  ai)ovo  a  hori/contal  mahogany  stand  ;  in  front  of  the  poles 
of  this  magnet — oi',  more  correctly  speaking,  magneto-electric 
inductor — islixed  to  the  stand  in  a  vertical  j)lanc  a  circular  brass 
ring,  over  which  is  stretched  a  mcml)rane,  carrying  at  its  centre 
a  small  oblong  jiicce  of  soft  iron,  which  plays  in  front  of  the  in- 


'  iMiu'liiecriiii;,  I"-". 


102 


THE   SPEAKING   TELEPUONE. 


'Inctor  mapfnet  wlienever  the  membrane  is  in  a  state  of  viliration. 
'I'liis  membrane  can  be  tightened  like  a  drum  l)y  tli(!  three  mill 
lieaded  screws  shown  in  the  drawing.  The  ends  of  the  coil  sur- 
rounding the  magnet  terminate  in  two  binding-screws,  by  which 
the  instrument  is  i)ut  in  circuit  with  the  receiving  instrument, 
which  is  shown  in  fig.  61.  This  instrument  is  nothing  more 
than  one  of  the  ttibular  elcetro-magnets  invented  by  M.  Nicies 
in  the  year  1852,  but  which  has  been  reinvented  under  various 
fancy  names  several  times  since.  It  consists  of  a  vertical  bar 
electro-magnet  inclosed  in  a  tube  of  soft  iron,  by  which  its  mag- 
netic field  is  condensed  and  its  attractive  power  within  that  area 
increased.  Over  this  is  fixed,  attached  by  a  screw  at  a  point 
near  its  cii'cnmfercnce,  a  thin  sheet  irc.n  armature,  of  the  thick- 
ness of  a  sheet  of  cartridge  pajjjr,  and  this,  when  under  the 
influence  oi  the  transmitted  currents,  acts  partly  as  a  vil)rator 
and  partly  as  a  resonator.  The  magnet  with  its  armature  is 
mounted  upon  a  little  bridge,  which  is  attached  to  a  mahogany 
stand  similar  to  that  of  the  transmitting  instrument 

The  action  of  the  ai)paratus  is  as  follows:  When  a  note  or  a 
word  is  sounded  into  the  mouthpiece  of  the  transmitter,  its  mem- 
brane vibrates  in  unison  with  tiie  sound,,  and  in  doing  so  carries 
the  soft  iron  indut-tor  attached  to  it  backwards  and  forwards  in 
presence  of  the  electro-magnet,  inducing  a  series  of  magneto-elec- 
tric currents  in  its  surrounding  helix,  which  are  transmitted  by 
the  conducting  wire  to  the  receiving  instrument,  and  a  con-e- 
sponding  vibration  is  therefore  set  up  in  the  thin  iron  armature 
sufficient  to  ])roiluce  sonorous  vibrations,  by  which  articidated 
words  can  be  distinctly  and  clearly  recognized.  In  all  previous 
attempts  at  producing  this  result  the  vibrations  were  produced 
by  a  make  and  break  arrangement ;  so  that,  while  the  number  of 
vibrations  per  second,  as  well  as  the  time  measures,  were  correctly 
transmitted,  there  was  no  variation  in  the  strength  of  the  cur- 
rent, whereby  the  quality  of  tone  was  also  recorded.  This  de- 
fect did  not  prevent  the  transmission  of  pure  musical  notes,  nor 
even  the  discord  ])roduced  by  a  mixture  of  them,  but  the  com- 
plicated variation  of  tone,  of  <|uality,  and  of  modulation,  which 


WORKIXG   OVKU   AUTIFICIAL    LINK. 


103 


make  lip  tlie  human  voice,  required  8onietliing  more  than  a  mere 
isochronism  of  vibratory  impulses. 

In  Mr.  Bell's  apparatus  not  (mly  are  th(!  vilirations  in  the 
receiving  instrument  isochronous  with  those  of  the  tran.smitting 
membrane,  but  they  arc,  at  the  same  time,  similar  in  ({ualit}''  to 
the  sound  producing  them  ;  for,  the  currents  being  induced  by  an 
hiductor  vibrating  with  the  voice,  differences  of  am[)litude  of 
vibration  c;inse  differences  in  strength  of  the  impulses,  and  the 
articulate  sound  as  of  a  person  speaking  is  produced  at  the  other 
end. 

1  Th(!  telephone  has  been  regarded  as  a  toy,  or  a  curiosity  to  be 
played  with  ;  but,  while  it  is  undoubtedly  extremely  interesting 
as  a  novelty,  it  is  very  much  more  than  ,iiis;  it  is,  scientifically 
and  practically,  a  great  success.  Tliere  are,  undoubtedly,  diffi- 
culties in  its  use,  but,  considering  that  it  is  a  contrivance  but  of 
yestenhiy,  the  wonder  is  that  it  is  so  perfect. 

When  a  telegraphist  ".rst  gets  into  his  hand  this  beautifully 
simple  and  electrically  delicate  instrument,  his  first  inclination  is 
to  test  its  carrying  power.  This  is,  of  course,  a  closet  experiment, 
not  working  with  actuid  telegraph  line,  but  with  a  resistance  coil 
equivalent  to  a  telegraph  line  of  stated  length.  An  experiment 
of  this  nature  gives  Ijctter  results  than  could  be  obtained  by  a 
veritable  line,  because  the  insulation  is,  so  to  speak,  perfect.  No 
leakage  at  undesigned  points  of  contact,  or  disturliance  from  un- 
favorable atmos[)heric  conditions,  is  felt,  and  the  experiment  is 
entirely  under  the  observer's  control.  The  apparatus  used  is 
designed  to  offer  the  .sime  lal)or  for  the  electric  current  to  over- 
come as  woidd  be  ollered  by  a  stateil  length  of  outside  telegraph 
line,  'iliis  artificial  resistance  is  nicely  graduated,  and,  as  the 
method  of  testing  was  suggested  by  Ohm,  a  German  electrician, 
the  unit  of  resistance  is  termeil  an  ohm.  Removing  the  tele- 
I)hone  to  such  a  distance  that  the  two  observers  wen;  out  of  ear- 
shot, the  test  with  resistance  was  tried,  and  with  a  resistanc(!  of 
1,000  ohms — roughly  speaking,  e([ual  to  seventy  miles  of  a  well 
constructed  line — the  sound  was  perfect,  although  not  very  loud. 


I  Climiihers'  .liiinial. 


104 


THE   SPEAKING  TELKPHONE. 


Kvery  .irtionlation  of  tlio  speaker  at  the  other  end  could  he  dis- 
tinguislicd  s(j  long  as  silence  was  maintained  in  the  room,  or  so 
l(jng  as  no  heavy  lorry  rumbling  over  the  stones  outside  sent  in 
no  liarsli  noise  which  drowned  the  faint  w]iis})er  of  the  instru- 
ment. The  resistance  was  gradually  raised  to  4,000  ohms — 
nearly  800  miles — with  like  favorable  results  ;  and  for  some  lit- 
tle distance  beyond,  articulation  could  still  be  made  out.  But  by 
the  time  10,000  ohms  had  been  applied,  ])uttiiig  the  speaker  at  a 
distance  of,  say,  700  miles,  sound  only,  but  not  articulate  sound, 
reached  the  car.  The  tone  was  there,  and  every  inflection  of  the 
voice  could  be  followed,  but  articulaticn  was  absent,  although 
the  listener  strained  every  nerve  to  catch  the  sound,  while  the 
s]ieaker,  as  was  afterwards  ascertained,  was  shouting  in  a  loud, 
clear  voice.  The  prolonged  notes  of  an  air  sung  could  be  heard 
with  the  resistance,  but  again  no  words  could  be  distinguished. 

The  next  experiment  was  to  join  uj)  the  telephones  in  the 
olHce  with  diirei'cnt  line  wires  in  succession  going  to  various 
distances,  and  working  with  different  kinds  of  telegraph  in.stru- 
ments.  When  this  was  done,  the  real  obstacle  to  teleplionic 
progress  at  once  asserted  itself  in  the  shape  of  induction.  The 
first  wire  experimented  with  was  2)artly  overhouso  and  partly 
underground,  and  the  offices  ujjou  it  were  working  Wheatstone's 
step-by-step  dial  instruments.  It  is  difficult  to  render  clear  to 
the  person  ignorant  of  telegraphic  ])henomcna  the  idea  exi)ressed 
by  the  word  induction.  Brit'llv,  it  maybe  }nit  thus  :  that,  when 
aa  electric  current  is  passing  on  a  wire,  it  has  the  faculty  of 
setting  up  a  current  of  opposite  character  in  any  wire  in  its 
vicinity. 

In  various  recent  articles  on  the  telephone,  mention  has  l)eon 
made  of  contact  as  the  cause  of  disturbance.  This  wonl,  how- 
ever, althougli  it  has  been  used  by  telegraphists,  is  misleading, 
and  can  only  be  used  as  an  endeavor  to  express  popularly  an 
electric  fact.  Actual  contact  of  one  wire;  with  another  would 
spoil  the  business  altogether.  A  wire  bearing  an  electric  cur- 
rent seems  to  be  for  the  time  surrounded,  to  an  undefined  dis- 
tance, by  an  electric  atmosphere,  and  all  wires  coming  within 


DIFFICULTIES   FROM   INDUCTION. 


105 


this  .atmospiiprc  have  a  piirrent  in  an  opposite  direction  set  up  in 
them.  Tiiis  i.s  as  near  an  exphination  of  the  ])henornena  of  in- 
duction as  thi!  state  of  telograpli  science  ut  present  affords.  Now, 
tlie  telephone  worlcs  with  a  very  delicate  nia<fnetic  current,  and 
is  easily  overpowered  by  the  action  of  a  .stronger  curnint  in  any 
wire  near  which  the  tolci)hone  wire  may  come.  To  work  prop- 
erly, it  nvpiircs  a  sih-nt  line. 

In  the  place  where  tlie  ob-sei-vations  were  made,  there  were  a 
large  number  of  wires  traviilling  under  the  floor,  along  passages 
to  the  battery  room,  and  to  a  ])ole  on  the  outside,  whence  they 
radiate;  or  out  to  a  jjipe  uiiilerground,  where  many  gutta-perctha 
covered  wires  lie  side  by  side.  On  applying  the  ear  t(j  ii  tele- 
phone joined  into  a  circuit  working  in  such  an  office,  a  curious 
sound  is  heard,  comjiarable  most  nearly  to  the  sound  of  a  pot 
l)()iling.  But  the  ])racticed  ear  could  .«oon  scnarato  the  boiling 
into  distinct  sounds.  There  was  one  mastcrlul  Morse  instru- 
ment— probably  on  the  wire  lying  nearest  tlu;  one  on  which  we 
were  joined  up — who.se  ])cremi)torv  click,  cli-i-i-ck,  click,  repre- 
senting dot,  dash,  dot  on  the  ])nnted  slip  we  read  from,  could 
be  heard  over  all.  Then  there  was  the  i;i])id  whir  of  a  fast  spee<l 
tran.smitter  sending  dots  and  dashes  at  express  speed  by  mechani- 
cal means;  and,  mo.st  curious  of  all,  the  rrrrr-op,  n'-op,  rrrrrrr- 
rrrrrr-op,  rrrrr-op,  rr-op  of  the  Wheatstono  dial  instrument,  the 
deadliest  fo(!  to  the  telephone  in  its  endeavors  to  gain  admission 
into  the  family  of  telegraph  in.stnmienK  There  may  be  reason 
in  this,  for  as  the  Wheat.stxme  dial  in.^trument  is  the  instrument 
us(>d  for  private  telegra]>hy,  or  for  the  least  important  i)ublic 
unices,  because  it  re(iuires  no  code  to  be  learned  by  the  manipu- 
lator, .so  it  woidd  likel)  be  the  first  to  be  displaced  if  an  acoustic 
tt'legra])h  jiermanently  took  the  field.  So  the  sentient  little 
Wlieatstone  dial  opens  it.s  mitrailleuse  fire  on  the  intruder,  on 
who.se  delicate  current.s,  in  the  words  of  an  accomplished  elec- 
trician, it  ])lay.4  old  Harry.  The  peculiar  character  of  the  sounds 
we  borrow  on  the  tele])1ionc  from  this  instrument  ari.ses  from  the 
fact  that,  as  the  needle  flies  round  the  dial,  a  distinct  current  or 
])ulsation  i:)as3cs  for  each  letter,  and  the  final  op  we  have  tried  to 


10»3 


THE    SPEAKING    TELEPHONE. 


roprcsoiit  shows  tlic  stoppa;.'!*  <)f  the  ncedlo  at  the  letters  as  words 
woro  spcllofl  o\it. 

It  iimst  not  1)0  understood  that  the  sounds  of  those  various 
instrniiieuts  are  actually  heard  in  the  telephone.  What  happens 
is,  that  the  currents  .stealin;^  ulonj^  th(^  telephone  wire  liy  induc- 
tion ])roduco  vilirations  in  the  diaphrajrni  of  that  instrument,  the 
little  nu'tal  ineud)rane  workinjr  on  the  niajruet  in  ready  response 
to  every  current. set  ui)l)y  the  latter.  When  it  isrenieniliered  that 
the  i)riiiciple  of  the  tele})houe  is  that  the  soun<l-eaused  vil)rations 
in  the  fllniy  diaphraj^m  at  one  end  create  similar  hut  magneti- 
cally-caused vibrations  in  the  diaphratnu  at  th<!  other  end,  and 
.so  rei)roduce  tlie  sound,  it  will  be  obvious  why  tiie  rapid  roll 
of  the  Wheatstone  dial  currents,  or  the  swift  sending  of  the 
fast-sj)ced  transmitter,  when  brought  by  induction  into  the  tole- 
[>honc  wire,  cause  disturbances  in  the  sound  vibrations,  and 
th<>reby  cripple  the  instrument  One  instnnuent  of  either  kind 
named  would  have  a  certain  efTect,  but  one  Morse  would  not 
have  any  greatly  ])rojudicial  effect.  But  a  nuinlicr  of  Morses 
going  together,  such  as  were  heard  in  our  exi)eriments,  would 
cond)inc  to  be  nearly  as  bad  as  onc^  W^heatstonc  dial  or  fast- 
speed  Monse.  So  delicate  is  tlu^  diaphragm  to  sound  (and  neces- 
sarily so)  that,  in  all  experiments  with  the  telephone  itself,  every 
sound  from  without  broke  in.  giving  eilect  like  the  well-known 
niunuur  of  the  shell. 

Joining  up  our  wire  now  to  a  more  ilistant  station  at  .sonu^ 
miles  along  the  railway,  and  having  on  its  poles  a  nundier  of 
wdiat  are  known  as  heavy  circuits,  the  ])ot-iK)iling  sound  assumeil 
even  more  marked  characteristics.  The  Wlu-aistone  dial  n<) 
longer  alh'cted  \is  ;  but  a  number  of  Morse  instruments  were  in 
full  gear,  and  tlui  fast-speed  transmitter  was  al-so  at  work.  While 
we  were  listi>ning,  the  circuit  t<i  which  we  were  joinecl  began  to 
work,  and  the  elTect  was  literally  electrical.  Hitherto  we  had 
only  borrowecl  currents — or,  seeing  they  were  so  unwelcome,  we 
might  call  them  cuiTcnts  thrust  upon  us — and  the  sounds,  though 
.sharp  and  inces.sant  were  gentle  and  rather  low.  But,  wIkmi  the 
strong  current  was  set  up  in  the  wire  itself,  the  listener  wlio  held 


INTEXSK   EFFECTS   OF    IXniTCTIOX. 


107 


one  of  our  telephones  nearly  jumped  from  the  floor  when  an 
iiii<^rv  pit-pat.  pit-pat,  pit-pat  pit  assailed  his  ear,  eausinj^  him  to 
(h'oj)  tiie  instrument  as  if  lie  had  been  shot.  It  was  a  result 
none  of  us  had  expected,  for  it  did  not  seem  possible  that  the 
delicate  metal  diai)hragni  and  the  little  maj^net  of  the  telephone 
could  produce  a  sound  so  intense.  Of  course,  it  was  only  in- 
tense when  the  ear  was  held  close  to  tl'.e  orifice  of  the  instrument. 
Held  in  the  hand  away  from  the  ear,  the  telephone  now  made  a 
first  rate  sounder,  and  we  could  tell  without  dilliculty  not  oidy 
the  sign.ils  that  were  passing,  but  found  in  it  a  more  condV)rtable 
tone  than  that  given  by  the  Morse  sounder  in  common  \ise. 

Other  experiments  of  a  like  ciiaracter  led  to  results  so  similar 
that  they  may  be  left  unnoticed;  and  we  proceed  now  to 
describe  one  of  a  diiferoit  character,  designed  to  test  the  tele- 
phone itself.  At  a  distance  of  about  half  a  mile,  access  was  ob- 
tained to  a  Morse  instrument  in  [)rivate  use,  and  joined  to  the 
ofTice  by  overhouse  wire.  Dividing  our  ])arty  and  arranging  a 
programme  of  operation,  two  remained  with  a  telephone  in  the 
office,  while  other  two,  of  whom  the  writer  was  one,  proceeded 
with  the  second  telei)hone  to  the  ilistant  instrument.  IJy  an  ar- 
rangement which  a  prai-tical  telegraphist  will  understand,  the 
key  of  the  Morse  was  kept  in  circuit,  so  that  signals  could 
be  exchanged  in  that  way.  It  may  be  noticed,  however,  that 
this  was  hardly  necessary,  as  the  iliaphragm  of  the  telej)hone 
can  be  used  as  a  key,  witli  the  linger  or  a  blunt  point,  so 
that  dot  and  dash  signals  are  interchangeable,  should  the 
voice  fail  to  be  heard.  As  the  wire  in  this  instance  travelled 
almost  alone  over  part  of  its  course,  we  were  in  hopes  that 
induced  currents  would  be  conspicuous  by  their  absence.  In 
this  we  were,  however,  disappointed,  for  the  j)ot  was  boiling 
away,  rather  more  faintly,  but  with  the  plop-plop  plop  distinctly 
audible,  and  (mee  more  a  shaq)  masterful  Mor.si;  click  was 
heard  coming  in  now  and  again.  The  deadly  Wlu>atstone  dial 
was,  however,  absent,  so  that  our  experiment  ])roved  highly  suc- 
cessful. For  some  rea.son  or  another — jirobably  an  imperfect 
condition  of  the  wire,  or  the  efTeets  of  induction  over  and  above 


108 


TlIK   SPEAKING   TKLKI'HONE. 


what  inado  itself  an(lil)lc  to  us — tlic  si)oken  sounds  wore  deficient 
in  distinctness:  but  souffs  sunjjf  at  either  end  were  verv  beauti- 
fully lieunl,  and,  indeed,  the  sustained  note  of  sunjf  words  had 
always  a  better  carrying  ])o\ver  than  ra[)idly  spoken  words. 
Every  syllable  and  every  turn  of  melody  of  such  u  song  as 
■•  My  Mother  liids  me  Bind  my  Hair,"  sung  by  a  lady  at  oiu'  end, 
or  "  When  the  Heart  of  a  Man,"  sung  at  the  other,  could  lie 
distinctly  heard,  but  with  the  elleet  before  noticed,  that  the  voice 
was  mullled  or  shut  in,  as  if  the  singer  were  in  a  cellar,  while  it 
was  not  always  jiossible  to  say  at  once  whether  the  voice  was 
that  of  a  man  oi"  a  woman. 

In  the  course  of  some  domestic  experiments  it  was  remarkcvl 
that,  in  playing  the  scale  downward  from  C  in  alt  on  the  piano, 
the  result  to  the  listener  was  a  tit  only  for  the  four  ujiper  notes, 
although  all  bcjow  that  had  a  clear  ting,  and  the  octaves  below 
were  mostly  distinct,  although  at  the  low  notes  of  the  ])iauo  i!ic 
sound  was  again  lost.  The  ringing  notes  of  a  m.isical  box  were 
not  .'^o  successful,  but,  with  close  attention,  its  rajiid  execution  of 
'•  Tommy  Dodil  "  could  be  well  enough  made  out.  An  en<leavor 
was  made  to  catch  the  ticking  of  a  watch,  l)ut  this  was  not  suc- 
cessful, and  the  experiment  is  not  n-conmicnded,  as  the  near 
presence  of  a  watch  to  a  magnet  is  not  ilesiralile:  ami  the  watch 
t'Xj)oscd  to  it  in  this  instance  was,  it  is  thought,  alfectcd  for  a 
short  time  thereafter,  although  it  received  no  permanent  damage. 

The  observations  made  in  the  course  of  these  experiments 
convinced  those  ]  resent  that  the  telephone  presents  facilities  for 
the  dangerous  practice  of  tapi)ing  the  wire,  which  may  make  it 
useful  or  dangerous,  according  as  it  is  used  for  ])ro])er  or  im- 
proper ])ur])oses.  It  might  be  an  important  addition  for  a  mili- 
tary commander  to  nuike  to  his  living  cavalry;  as  an  expert 
sound  reader,  accompanying  a  column  to  cut  oil  the  eiu'my"s 
telegra])h  connections,  might  jn-eecdc  the  act  of  destruction  bv 
robbing  him  of  some  of  his  secrets.  The  ra])iditv  and  sim- 
plicity of  the  means  liy  which  a  \\\\v  conld  be  milked,  without 
being  cut  or  ])Ut  out  of  circuit,  struck  the  whole  of  the  jiartv 
engaged   in   the  various  trials   that  are   described  above.     Of 


TUOMSON'S  TKI-EJMION'IC    KXI'KHIMKN'Trf. 


109 


course,  tlio  ]>rocoss  n[  tiippiiifr  liy  t('l(']ilioiu>  <'nMl(l  not  lie  carricil 
(lilt  if  the  iiistniiiu'iit  in  use  was  a  WlioatstoiK!  dial  <ir  siiiul(» 
iii'i'illi',  or  if  the  wire  was  licin.u'  worknl  duplex  or  with  a  last 
speed  Morse,  for  in  tliese  eases  the  sounds  ai'e  too  rapid  or  too 
iu(h'linite  to  he  read  hy  ear.  'I'he  dau^/er  is  thus  limited  to  ordi- 
nary soun<ler  or  Morse  telejiraplis ;  hut  these  still  form  the  main- 
stay of  every  puhlie  system. 

Sinco  the  trials  hen;  de.scrihed  were  made,  the  newspapers 
have  recorded  a  beautiful  application,  hy  Sir  William  Thomson, 
of  the  eleetrie  ])art  of  the  teleplioiie  to  exhiliit  at  a  distance  the 
motions  of  an  anemometer,  the  ohject  heinir  to  show  tlu'  force  of 
air  euri'eiits  in  coal  mines.  This  is  a  useful  appli<-atioii  of  an 
electric  fact,  and  doubtless  points  the  way  to  fui'tlu'r  discoveries. 
But  it  is  to  be  noticed  that  the  experiment,  interestin<^  as  it  i.s, 
hardly  comes  under  the  head  of  tele])hony.  what  is  rejinxbtecd 
at  a  distance  bein^f  not  sound,  l»ut  motion. 

Obviously  the  invention  cannot  rest  where  it  is;  and  no  one 
more  readily  than  the  practical  tele^M-aphist  will  welcome  an 
in.strunient  at  once  simple,  direct  and  reliable.  Kven  in  its 
present  form  the  telephone  may  l)e  suee(>ssfully  us(m1  where  its 
wire  is  absolutely  isolated  from  all  other  tele<i;ra])h  wires.  But  tlu; 
general  impression  is  that  its  povter  of  reproducing  the  .xound 
must  ])e  intensilied  before  its  use  can  become  general,  or  come 
up  to  the  popular  expectation. 


CIIAPTKR  IV. 

HISTORY   OK  TlIK    I'RODUCTION   OF   GALVANIC   MUSIC. 

This  clifiptor  will  he  devoted  to  the  history  of  the  pvodnotion 
of  galvanic  music,  and  to  the  reproduction  of  sounds  by  elec- 
tricity, from  the  experiments  of  Page,  in  1837,  to  those  of  Gray, 
in  1874.    The  authorities  quoted  are  given  in  chronological  order. 

1  The  following  cxporimont  was  connnunicatcd  by  Dr.  C.  G. 
Pago,  of  Salem,  Mass.,  in  a  recent  letter  to  the  editor.  From  the 
well  known  action  upon  masses  of  matter,  wln-n  one  of  those 
masses  is  a  magnet  and  the  other  some;  eoniliieting  substance, 
transmitting  a  galvanic  current,  it  might  have  been  safely  infer- 
red {a  jyriori)^  that  it  this  action  were  prevented  by  having  both 
bodies  pennanently  lixed.  a  molecular  derangement  would  occur 
whenever  such  a  reciprocal  action  should  be  established  or  de- 
stroyed. This  condition  is  fully  proved  by  the  following  singular 
experiment.  A  long  co])i)er  wire,  covered  with  cotton,  was 
wound  tightly  into  a  flat  spiral.  After  making  forty  turns,  the 
whole  was  firmly  fixed  by  a  smearing  of  common  cement,  and 
mounted  vertically  between  two  upright  supports.  The  ends  of 
the  wire  were  then  brought  down  into  mercury  cups,  v:hich  were 
connected  by  eojijier  wires  with  the  cups  of  the  bat<  "'v,  which 
was  a  single  pair  of  zinc  and  lead  ])lates,  excited  by  sa'|  ?  .ite  of 
copper.  \V1ien  one  of  the  connecting  wires  was  lifted  from  its 
cup,  a  bright  sj)ark  a. id  loud  snap  were  j)roduced.  When  one 
or  both  jtoles  of  a  large  horseshoe  inngiiet  are  brought  'ly  the 
side  or  put  astride  the  spiral,  but  not  touching  it,  a  distinct  ring- 
ing is  heard  in  the  magnet  as  often  as  the  battery  connection 
with  the  spiral  is  made  or  broken  by  one  of  the  wires.  Thinking 
that  the  ringing  sound  might  be  jirodueed  by  agitation  or 
reverberation  from  the  snap,  1  liad  the  battei-y  contact  broken  in 
a  cu]i,  at  considerable  distance  from  the  field  of  experiment:  tlie 
effi>ct  wiis  the  same  as  before.     The  ringing  is  heard  both  when 


1  C.  G.  PuKC,  Silliiuuu's  Jcjurnul,  vol.  xxxii.,  p.  3iMi,  July,  1S.'37. 


TONKS   PRODUCED   «V    KLECTKICAli   CIRKENTS. 


Ill 


the  contuct  is  made  imd  In-oken  ;  when  tlie  contact  is  made,  tiio 
sound  emitted  is  very  feeble ;  wlion  l)i'okoii,  it  may  he  heard  at  two 
or  three  feet  distance.  The  exj)erimf'iit  will  hardly  succeed  with 
small  magnets.  The  first  used  in  tiic  exjieriment  consisted  of 
three  horseshoes,  supporting  ten  pounds.  The  next  one  tried 
was  compo.sed  of  six  magnets,  su])porting  fifteen  pounds  by  the 
armature.  The  third  suppoi't(>d  two  jiound.s.  In  each  of  these 
trials  the  .sounds  produced  differed  from  each  other,  and  were  the 
notes  or  pitches  jiecnliar  t(j  the  several  magnets.  If  a  large 
magnet  supported  by  the  bend  be  struck  with  the  knuckle,  it 
gives  a  musical  note ;  if  it  be  slightly  tapped  with  the  finger  nail, 
it  returns  two  sounds,  one  its  pro])er  musical  pitch,  and  another 
an  octave  above  this,  which  last  is  the  note  given  in  the  ex})eri- 
ment 

ox  THE   DISTURBANCE   OF   MOLECULAR   FORCP:.S  BY   MAGXETLSM. 

*  A  .short  article  on  this  subject  appeared  in  the  last  number  of 
this  journal  under  the  caption,  ''  Galvanic  Music."  The  following 
experiment  (as  witnessed  by  yourself  and  others  not  long  since; 
ailords  a  striking  illustration  of  the  curious  fact,  that  a  ringing 
.sound  accompanies  the  disturbance  of  the  magnetic  forces  of  a 
steel  bar,  provided  that  bar  is  so  poised  or  su.sjiended  as  to  ex- 
hibit acoustic  vibrations.  An  electro- magnetic  bar  four  and  a 
half  inches  in  length,  making  five  or  six  thousantl  revolutions 
})er  minute,  near  the  poles  of  two  horseshoe  magnets  properly 
suspended,  produces  such  a  rapid  succession  of  disturljanecs  that 
the  sound  becomes  continuous  and  much  more  audible  than  in 
the  former  experiment,  where  only  a  single  vibration  was  pro- 
duced at  a  time. 


TOXKS   I'RODUCEI)    HV   ELECTRICAL   CURRENT.S. 

2  Mr.  Page  was  the  first  to  discover  that  an  iron  bar,  at  the 
moment  it  became  magnetic  through  the  galvanic  current,  gave 
a  ])eculiar  tone,  and  this  fact  has  since  been  confirmed  by  Mr. 
Delezennc. 


1  C.  0.  Piitfi',  SiHiniairs  .loiinial,  vol,  xxxiii.,  p.  Us,  ()otiil)or,  l^rit. 

»  W.  Werthuiiii.     Auimleii  dur  I'liysio  uiul  Chomio.     L.WVIt,  .luiiu,  ISiy. 


112 


THK   SI'EAKINCr   TELEPHONE. 


Without  being awaro  of  tliis  discovciy,  I  publislied,  in  1844,  a 
trcntiso  in  wliicli  I  dealt  witli  several  (juestioiis  relating  to  this 
subjeet.     In  this  work  I  attempted  to  prove : 

1st.  That  the  elcetrieal  eurrent  eauses  a  temporai'v  weakening 
of  the  eoeflieient  of  the  elastieity  of  iron. 

2d.  That  likewis(>.  tlie  magnetization  is  aeoompanied  by  a  very 
slight  deerease  of  the  eoeflieient  of  the  elastieity  of  the  iron,  which 
diminishes  only  ])artially  when  the  magnetizing  cnrrent  is  inter- 
rupted, and  tliat  this  result  does  not  manifest  itself  at  onee,  but 
only  upon  the  continued  action  of  the  currents. 

The  production  of  sound  thnnigh  the  outside  current  (that  is, 
{[  current  wliieh  ]ias.ses  through  a  helix  in  whose  axis  is  an  iron 
bar  or  extended  iron  wire)  was  lirst  accurately  noticeil  by  Mr. 
Marrian. 

According  to  these  physici.sts,  the  sound  |)roduceil  was  identical 
with  that  obtaineil  by  striking  the  rod  on  eillu'r  <if  its  ends  in  the 
direction  of  its  axis.  Striking  the  rod  sideways,  liowcver,  did 
not  give  the  same  n^sult. 

Mr.  ^larrian  also  noticed  that  other  metals,  under  the  same  con- 
ditions as  iron,  did  not  give  any  sound,  an<l  tliat  the  soumls  from 
rods  of  the  same  dimensions,  wdiethcr  of  iron,  tempered  steel  or 
magnetized  steel,  were  idcnti(;al. 

^[r.  Matteueci  lias  repeated  these  exiieriments  with  wires  as  well 
as  iron  1  lars,  attempting  especially  to  establish  the  relation  between 
the  strcngtii  of  the  current  and  the  intensity  of  the  sounds.  lie 
has,  however,  been  in  some  doubt  as  to  tlu;  eharactei-  and  value 
of  the  sounds. 

Messr.«.  l)e  la  Rive  and  Rcatson  individually  made  the  dis- 
covery that  the  current  which  ])asses  directly  through  an  iron 
wire  produces  a  sound  therein.  In  one  of  his  later  tre.  tise.s,  ^[r. 
De  la  liive  has  given  a  minute  do-eription  of  a  series  of  experi- 
ments with  various  combined  c  .ents  on  dillerent  metals  and 
under  difTerent  conditions. 

Mr.  Guillemcn  made  an  interesting  experimcMit,  tlu-  result  of 
wliieh  conlirms  my  experiments  already  mentioned.  He  found 
that  a  weak  iron  bar  which,  surrounded  by  a  helix,  is  lixed  at 


TONES   I'HODUCEl)   HY   ELECTRICAL   CURRENTS. 


113 


one  of  its  ends  in  ii  horizontal  position  and  at  the  other  ond  is 
loaded  with  a  li^'iit  weight,  visil)lv  straightens  itself  wlien  a  cur- 
rent })asses  tiu'ough  the  helix.  Mr.  (inillenien  attril>ntes  this 
movement  to  a  temiiorarv  increase  ol!  the  elasticity  of  tiie  iron 
effected  liy  magnetization. 

vVt  the  same  time  I  delivered  to  the  academy  a  short  note,  in 
which,  without  entering  into  the  details  of  the  experiments,  1 
explained  the  results  wiiidi  I  had  obtained,  and  how.  according 
to  my  opinion,  the  .sounds  were  to  he  accounted  for.  The  pres- 
ent treatise  contains  develoiiments  and  proofs  to  sustain  the 
opinions  given  l>y  me  at  that  time.  Jt  seems  superfluous  to 
repeat  here  the  discussion  wliich  occurreil  at  the  time  of  writing 
this  note,  between  Ak'ssrs.  De  laliive,  (luillcmfn  and  Wartmann. 
I  desire  simply  to  say  that  the  last  named  scientist  was  the  lirst 
to  notice  that  a  current  passing  through  a  wire  may  ])roduce  a 
sound  without  then;  being,  in  the  wire,  a  resistance  of  any  amount 
to  oppo.se.  Sound  may  therefore  be  produced  as  well  in  an  iron 
bar  as  in  an  extended  iron  wire,  heat  having  only  an  insignili- 
cant  ])art  to  jilay  in  the  phenomenon. 

Later  on  Mr.  De  laEive  senta  treati.«c  to  the  Royal  Society,  in 
London,  which  dealt  with  a  jiart  of  this  subject.  After  admit- 
ting that  no  .sound  is  producc(l  ly  ;i  current  pa.ssing  through  any 
metal,  other  than  iron,  he  goes  on  to  describe  a  new  class  of  facts. 

All  conductors,  when  expo.scd  to  the  inlluence  of  a  powerful 
electro-magnet,  give,  at  the  moment  of  the  jia.s.sage  of  an  inter- 
rupted electrical  current,  a  very  distinct  sound,  similar  to  that  of 
Savart's  cogged  wheel.  Tlie  influence  of  magnetism  on  all  con- 
ducting bodies  .seems  to  c;onsi,st  in  its  imparting  to  the  latter, 
similar  })roperties  to  tho.se  possessed  by  iron  in  it.self :  thus  devel- 
oping in  these  conductors  tiie  pro])erty  of  emitting  sounds  whicii 
are  shnilar  to  those  given  l)y  iron  and  other  metals  without  aid 
from  the  action  of  a  magnet. 

VIURaTIONS  of  TKEVELVAN'.S  BAHS  1!V  'I'IIK  (lALVANIC  crUUKXT. 

*  The  vibrations  of  Trevelyan's  bars  l)y  the  action  of  heat  i.s 
an  experiment  more  interesting  than  familiar,  and  one  whicli 

»  Silliimm's  Journal,  1850.     Vol.  ix.,  p.  lO."). 


114 


THE   .Sl'EAKIXa  TEI.EJMIONE. 


has  boon  variously  and  vaguely  exj)laii)od  by  most  authors.  It 
will  not  be  necessary  for  nie  to  reea[)itulate  the  several  deserip- 
tions  and  solutions  of  this  phenomenon,  as  the  novel  experi- 
ment about  to  be  detailed  will  embrace  substantially  the  whole 
subject. 

About  a  year  since,  while  exhibiting  to  a  cla.ss  the  vibration 
of  these  bars  by  heat,  it  became  inciuiveiiient  to  prolong  the  ex- 
j)eriment,  as  the  vil)ration  ceases  as  .>^oon  as  the  temperature  of 
the  bar  is  somewhat  reduced,  and  1  was  induced  to  .seek  for 
some  method  by  which  the  vibratory  motion  could  l)c  produced 
and  continued  at  i)leasure  without  the  trouble  of  reheating  the 
bars  for  each  trial.  Ai'ter  various  fruith'ss  etforts,  [obtained  a 
most  beautiful  result  by  using  the  heating  power  of  a  galvanic 


Fitj.  02. 

current  Fig.  62  shows  the  mode  of  ])erforming  the  experi- 
ment with  the  battery.  .V  ;nid  ]?  arc  the  two  forms  usually  given 
to  Trevelyan's  bars,  which,  when  to  be  vibrated  by  the  action 
of  heat,  are  made  of  brass,  aiul  weighing  from  one  to  two 
liound.s,  and  after  being  sufTiciently  heated  are  placed  u])on  a 
cold  block  of  lead,  as  seen  in  lig.  iS'.].  The  two  bars  may  be 
])laccd  u])on  the  same  block,  though  the  vibrations  are  apt  to 
interfere  when  two  are  used.  When  the  Iwirs  are  to  vibrate  by 
the  galvanic  current,  they  may  bi;  ot  the  same  size  and  form  a3 
shown,  and  of  any  kind  of  metal — brass,  or  cojjper,  or  iron,  how- 
ever, seeniing  to  be  most  convenient.  One  or  both  of  the  bars 
may  be  ])laced  at  once,  without  reference  to  temperature,  u])on 
the  stand,  as  in  fig.  62,  the  bars  resting  upon  metallic  rails  E  F, 


trevp:lyan'  s  experiment. 


115 


which  latter  are  made  to  communicate  each  witli  the  poles  of  a 
galvanic  battery  of  some  conHiderable  heating  power.  Two 
j)airs  of  Daniell's,  of  Smoe's,  or  of  Grove's  battery  of  large  size 
are  sufTicient.  Tiie  battery  I  em])loy  consists  of  two  pairs  of 
Grove's,  with  ])lat!nuin  plates  four  iiiclies  scjuare.  'J'he  vibration 
will  ])rocccd  with  great  ra}>idity  as  long  as  the  galvanic  current 
is  sustained. 

In  lig.  68  one  ]w>le  of  the  Ijattery  is  connected  with  the  metallic 
block,  and  the  other  pole  with  mercury  in  a  little  cavity  in  the 
centre  of  the  vibrating  bar.  Tlie  ex})eriment  succeeds  much 
better  with  the  rails  as  in  fig.  02,  and  quite  a  number  of  bars 
may  be  kept  in  mo+i(>;i  by  increasing  the  number  of  rails,  and 
l)assing  the  current  from  one  to  the  other  through  the  bars  rest- 
ing upon  them. 


Fig.  63. 

The  rails  are  best  made  of  brass  wire,  or  a  strip  of  sheet  brass, 
though  other  metals  will  answer — the  harder  metals  which  do 
not  oxidate  readily,  however,  being  i)referred.  A  soft  metal, 
like  lead,  is  not  so  favorable  to  the  vibrations  in  this  experi- 
ment, although  in  Trcvclyan's  (X])crimcnt  lead  seems  to  be 
almost  the  only  metal  that  will  answer  to  supi)ort  the  bar,  which 
is  usually  made  of  brass. 

Prof.  Graham  and  other  authors  have  attributed  the  vibration 
of  Trcvclyan's  bars  to  the  repulsion  between  heated  bodies,  and 
others  have  classed  the  jihenomenon  with  the  s|iheroidal  state  of 
heated  bodies.  I  do  not  consider  that  any  repulsive  action  is 
manifested  or  necessary  in  either  of  these  cases,  nor  do  1  know 
of  any  instance  in  which  a  repulsion  has  been  proved  between 
heated  bodies.  It  is  obvious  some  other  solution  is  required  for 
this  curious  phenomenon,  and  it  appears  to  me  that  the  motion 


116 


TUK   HI'EAKIXfl   'IKI-KI'lIONK. 


is  due  to  an  expansion  of  the  metallic  hlock  at  the  jioiiit  of  con- 
tact, and,  \i[Ht\i  this  supposition,  it  api)ears  plainly  why  a  block 
of  lead  is  rcipiired.  That  is,  a  metal  of  low  conductinj^  power 
and  high  expansibility  is  necessary,  and  lead  answers  these  con- 
ditions best  In  a  fiiture  communication  I  will  analyze  this 
matter  and  explain  more  fully. 

The  size  of  the  bars  may  be  very  nnich  increased  when  the 
galvanic  current  is  enij)loyed,  and  some  curious  motions  are  ob- 
served when  long  and  large  cylinders  of  metal  are  used.  If  they 
are  not  exactly  balanced,  which  is  almost  always  the  case,  they 
commence  a  slow  rolling  back  and  forth,  until  finally  they  roll 
entirely  over,  and  if  the  rails  were  made  ^-ery  long  they  would 


Fig.  G4. 

go  on  over  the  whole  length.  .\n  inclination  of  the  rails  is  re- 
quired in  this  case,  but  it  may  be  so  slight  as  not  to  be  jicrcep- 
tible  to  the  eye. 

If  a  long  rod  of  some  weight  l)e  placed  across  one  of  the  bars, 
as  shown  in  fig.  04,  the  vibrations  will  become  longer,  and  by  way 
of  amusement  I  have  illustrated  this  with  a  galvanic  see-saw,  as 
it  may  be  termed. 

It  is  well  hr.own  that  where  mere  contact  (without  metallic 
continuity)  is  made  by  metals  conveying  the  galvanic  current, 
the  metals  become  most  heated  at  the  ])oints  of  contact,  and  if  the 
current  be  frequently  broken  the  heat  at  these  points  is  still  more 
augmented.     It  is  for  this  reason  we  are  able  to  use  various 


MOLKCULAR   ACTION    OF   MAGXKTIC   ]iOJ)IES.  117 

kinds  of  metals  for  the  experiment,  witliout  reference  t(    tlieir 
conducting  powers  and  expansibilities. 


VIBRATORY  MOVEMENTS  AN'l)  MOLKCULAK  EFFECTS  DETER- 
MINED IN'  MAGXETIO  BODIES  liY  THE  INFLUENCE  OF  ELEC- 
TRIC  CURRENTS. 

^  Ml".  Page,  an  American  philosopher,  had  observed,  in  1837, 
that  on  bringing  a  liat  spiral,  traversed  by  an  eliT-trio  cui'rent, 
near  to  the  jiole  of  a  powerful  magnet,  a  sound  is  produced. 

M.  Delozen.ic,  in  France,  also  succeeded,  in  1838,  in  producing 
a  .sound  by  revolving  a  soft  iron  arnuiturc  ra})idlv  before  the 
poles  of  a  horseshoe  magnet.  In  1843,  I  niy.self  remarked  that 
plates  or  rods  of  iron  give  out  a  v(>ry  decided  sound  when  i)laced 
in  the  interior  of  a  helix  whoso  wire  is  ti'aversed  by  a  powerful 
olectrio  current;  l)iit  only  at  the  moment  when  the  circuit  is 
closed,  and  when  it  is  interrupted. 

Mr.  Ga.ssiot,  in  London,  and  Mr.  Marrian,  in  IJirniingham, 
had  also  maile  an  analogous  experiment  in  18-44.  Attril)Uting 
this  singular  ]ili(  nomenon  to  n  change;  brouglit  abmit  by  the 
magnetism  in  the  molecular  constitution  of  the  magnetized  body, 
I  wc'nt  through  a  great  number  ot  experiments,  in  order  to  study 
this  interesting  subject. 

It  is  above  all  things  im])ortant.  in  order  to  obtain  a  numerous 
.scries  of  vibrations,  to  be  provided  with  a  means  of  interrupting 
and  of  completing,  many  times  in  a  very  short  space  of  time,  the 
circuit  of  which  the  wire  that  transmits  the  current  forms  a  part; 
in  other  words,  to  render  a  current  discontinuous  or  continuous. 
With  this  view,  I  made  use  of  one  of  the  numerous  apparatus 
called  rheotomes,  or  cut-currents,  and  which  are  intended,  when 
place(l  ill  the  circuit,  to  render  a  curi-ent  discontinuous.  One 
of  the  most  convenient  (lig.  (I.j)  consists  of  a  hoi'i/.ontal  rod, 
carrving  two  nceiUcs,  inserted  perpcndiculai'ly  and  parallel  with 


'  Treatise  (111  Kleetl'ieily  in  Tlienrv  uiul  rriu'lice,  \<y  Aiii,'.  Du  In  Jlive.     I^.V,,    Vol. 
1;;;  [Mines  ;jiiO  til  :!^'l  ilielusive. 


118 


THK   Sl'EAKINCi  TKLEPHONE. 


each  other,  so  aiTanged  that  when  thoy  are  immersed  simultane- 
ously in  two  capsules  tilled  with  mercury,  and  insulated  from 
each  other,  the  circuit  is  closed;  and  when  they  are  not  immersed, 
it  is  oj)en.  A  clock  work  movement,  or  simply  a  winch  moved 
by  the  hand,  gives  a  rotatory  movement  to  the  axis;  whence  it 
follows  that,  in  a  given  time,  a  second  for  example,  the  circuit 
may  be  closed  or  interrupted  a  great  number  of  times.  The  ap- 
paratus of  fig.  65  presents  four  needles  instead  of  two,  and 
conserpiently  four  comj)artments  corresponding  with  the  four 
needles.  We  shall  have  occasion  hereafter  to  see  the  use  of  the 
second  system  of  two  needles ;  for  the  present,  a  single  one  is 
sufficient;  and,  conseqtiently,  in  all  the  experiments  that  will 
follow,  in  order  to  place  it  in  the  circuit,  we  shall  employ  indif- 
ferentlv  either  the  one  that  is  nearest  to  the  clock  work  move- 


Fig.  65. 

ment  or  the  oiio  that  is  most  distant.  There  is  a  risk  of  the 
mercury  being  projected  when  the  movement  is  too  rapid;  to 
I)revent  this  inconvenience,  we  must  cover  the  capsules,  the 
needles,  and  the  axis  that  carries  them,  with  a  small  glass  shade. 
When  tiie  current  is  very  ])owerful,  the  mercury  is  oxidized  by 
the  effect  of  the  sparks  tliat  occur  at  the  moment  when  the 
needles  emerge;  in  this  case  it  is  necessary  to  remove  the  oxide, 
or  to  change  the  mei'cury.  We  may  do  without  mercury,  and 
supply  its  place  by  two  elastii;  metal  plates  resting  on  a  cylinder, 
or  on  the  circumference  of  a  varnished  wooden  or  ivory  wheel, 
in  the  edges  of  which  are  inserted  small  ])icces  of  metal,  in  me- 
tiillic  communication  together.  When  the  elastic  j)lates,  by 
means  of  the  rotation  of  the  cylinder  or  of  the  wheel  upon  its 
axis,  come  in  contact  with  the  metal  2:iart  oF  the  surface,  the  eir- 


'S 


ELECTRICAL   RHEOTOMK. 


119 


110- 

oin 
ed, 
/cd 
it 
'uit 


ciiit  is  closed ;  when  the  contact  with  this  metal  part  ceases, 
which  oecure  when  the  contact  is  with  the  wood  or  ivory,  tlie 
circuit  is  open.  It  is  necessary  in  this  case  that  the  two  plates, 
as  were  tlie  mercury  cups  in  the  preceding  case,  shall  he  in  the 
conrse  of  the  circuit,  that  is,  to  traverse  the  wire  of  the  helix,  and 
shall  press  strongly  against  the  circumference. 

"We  may  also  interpose  in  the  course  of  the  current  merely  a 
toothed  wheel  ami  an  elastic  metal  plate,  which  jircsses  upon  the 
teeth  of  the  wheel  (lig.  66).  By  giving  the  wheel  a  movement 
upon  its  axis,  wo  cause  the  plate  to  leap  from  one  tooth  to 
another;  each  leap  produces  a  rupture  in  the  circuit,  which  is 
closed  again  immediately  afterwards.  The -musical  tone  given 
out  by  the  plate,  when  we  have  no  other  means  of  measuring  it, 
gives  us  exactly  the  number  of  times  that  the  circuit  has  been 
opened  and  closed,  that  is  to  say,  interrupted,  in  a  second.     I 


Mi/.  G6. 

have  dwelt  upon  these  several  kinds  of  rheotomes  because  we 
fre(|uently  make  use  of  one  or  the  other  of  them.  For  the  pres- 
ent, we  shall  ap])ly  them  to  the  study  of  the  vibratory  movement 
experienced  by  magnetic  bodies  under  the  influence  of  discon- 
tinuous currents. 

When  wo  ])laee  a  magnetic  but  unmagnetized  body,  .such  as 
iron  or  steel,  in  the  interior  of  a  bobbin,  this  body  experiences 
very  remarlcable  vibratory  movements,  as  soon  as  we  jiass  a  series 
of  discontinuous  currents  through  the  wire  with  which  the  bobbin 
is  encircled.  These  movements  are  made  manifest  undiM'  the 
form  of  very  decided  and  varied  sounds,  when  the  body  has  a 
cylindrical,  or  even  an  elongated  form.  The  sound  is  less  de- 
cided, but  more  sharp  and  more  mefcillic,  with  steel  than  it  is  with 
soft  iron.  Whatever  be  the  form  or  the  size  of  the  pieces  of  soft 
iron,  two  sounds  are  always  to  bo  distinguished ;  one  a  series  of 


120 


THE   Sl'KAKING  TELEl'IIONK. 


blows  or  sliockri,  more  or  less  dry,  and  very  analor;oiis  to  the 
noise  made  by  rain  when  falling  on  a  metal  roof;  these  blows 
exactly  correspond  to  the  alternations  ol'  the  passage  and  the  in- 
terruption of  the  current;  the  other  sound  is  a  musical  S(jund, 
corresponding  to  those  which  would  l»u  given  by  the  mass  of  inm, 
by  the  etfcct  of  the  transverse  vibrations.  We  must  uUve  c^are  in 
these  sounds  to  distinu;uisli  those  that  are  due  to  the  simple  me- 
chanical action  of  the  current  upon  the  iron — an  action  which, 
being  exercised  throughout  the  entire  mass,  may  deform  it,  ami 
consequently  ])roduce,  by  its  very  discontinuity,  a  succession  oF 
vibrations,     llowovcr,  this  is  not  sufficient  for  the  explanation  of 


Pig.  G7. 

all  the  sounds;  and  we  must  admit  that  there  is,  in  addition,  a 
molecular  action,  namely  that  the  magncti/.ation  (k'ci'iiiines  a 
particular  arrangement  oC  the  molecules  of  the  iron,  a  ra|)id  suc- 
cession of  iiiagnetizatioiis  and  dcningneti/ations  gives  lise  to  a 
series  of  vibrations.  How,  for  example,  can  we  otherwise  explain 
the  very  clear  and  brilliant  mnsical  sound  given  out  by  a  cylin- 
drical mass  of  iron  4  inches  in  diameter,  and  weighing  2"2  lbs., 
when  pla(^(,Ml  in  the  iuterioi'  of  a  larue  helix  (llg.  (!7).  while  tra- 
versed liy  a  diseontinuous  c\n-rcnt  ?  Rods  of  iron  half  an  inch  and 
ujjwards  in  diameter,  when  llxed  by  their  two  extremities,  also 


MOLECULAR  ACTION  OF  MAGNETIC   HODIEa 


121 


give  out  very  docided  sounds  under  tlio  same  influenco.  But  the 
most  brilliiint  sound  is  that  wliicli  isol)tained  by  stretching  upon 
a  souudinjr-boai'd  well  aiiiicidcd  wires,  (Hic  or  two  twentieths  of  an. 
inch  iu  diameter  and  a  yard  or  two  ni  length,  'i'iiey  are  j)laced 
in  tlie  axis  of  one  or  several  bobbins,  the  wires  of  which  arc 
traversed  by  electric  currents,  and  they  ])roduee  an  assemblage 
of  sounds,  the  efleet  (^f  which  is  surprising,  and  which  greatly 
rcsend)lcs  that  to  wliich  several  church  bells  give  rise  when 
vibrating  harmonically  in  the  distance.  In  order  to  obtain  this 
cllcet  it  i.s  necessary  that  the  succession  of  the  ein'rents  be  not 
too  rapid,  and  that  the  wires  be  not  too  liiglily  strained.  With 
a  win;  5  feet  2  inches  in  length,  and  j^^^  inches  in  diameter,  [ 
found  that  the  maximum  of  cil'ect  occurs  when  it  is  stretched  ])y 
a  weight  of  from  57  lbs.  to  117  lbs.,  if  it  is  annealed  ;  and  from 
6-ni)s.  to  126  lbs.,  if  it  is  hardened.  iJcvond  these  limit.-!,  in  pro- 
portion as  the  tension  increases,  the  total  intensity  and  tlie  num- 
ber of  dilTerent  sounds  notably  diminish  ;  and,  ata  certain  degree 
of  tension,  wc  no  longer  hear  the  sound  due  to  the  transverse 
vibrations,  but  simply  that  arising  from  the  longitudinal  vibra- 
tion.s.     ^J"he  ri'verse  oeeur.s  when  the  wire  is  slackened. 

Sounds  entirely  analogous  to  those  we  have  been  describing 
may  be  ]iroduccd  by  pa.ssing  the  discontinuous  electric  current 
through  the  iron  wire  itself.  "Wc  remark,  in  like  manner,  a  sc- 
ries of  dry  blow.-i,  corresponding  to  the  intcrruj)tions  of  the  cur- 
rent, and  stronger  and  more  sonorous  nnisical  sounds,  in  some 
cases,  than  those  that  are  obtained  by  the  magnetization  of  the 
wire  itse'lf.  ^J'liis  su})criority  of  efTcct  is  especially  manifested 
when  the  wire  is  well  aimealed,  and  of  a  diameter  of  about  one 
twelfth  of  an  inch;  for  greater  or  less  diameters,  the  magnetiza- 
tion.by  the  helix  produces  more  intense  eiTects  than  those  wdiich 
result  from  the  transmission  of  the  current,  ^^orcovcr,  the  same 
circumstances  that  inlhience  the  nature  and  the  force  of  the 
sound  in  the  former  case,  exercise  a  similar  iniluence  in  the 
latter.  The  transmission  of  the  discontinuous  current  produces 
sounds  only  when  transmitted  through  iron,  st(>cl,  argentine,  and 
magnetic  bodies  in  general ;  but  in  diilerent  degrees  for  each, 


122 


THE   SPEAKING   TEI.El'IION'^. 


depending  on  the  coorcitiv(!   force   that  opposes  the  plienom- 


cnoii. 


r 


Wires  oC  copper,  platinum,  silver,  and,  in  general,  any  metals, 
except  the  magnetic,  do  not  give  forth  any  Hoiiiid,  whether  under 
the  influence  of  transmitted  currents,  or  under  that  of  ambient 
currents,  such  .as  the  currents  that  traverse  the  convoluti;  'is  of 
a  wire  coiled  into  a  helix  around  a  bobliin.  Tiio  sound  t^.at  is 
produced  wlien  a  discontinuous  electric  current  is  made  to  pass 
in  an  iron  wire,  explains  a  fact  that  had  been  for  a  long  ])criod 
observed,  and  had  been  described  as  far  back  as  17S5,  by  the 
Canon  (Jottoin  de  Coma,  a  neighbor  and  a  contemporary  of 
Volta,  This  fact  is,  that  an  iron  wire  of  at  li-ast  ten  yards  in 
longtli,  when  stn^tchcd  in  tiic  ojien  air,  spontaneously  gives  foith 
a  sound  under  the  inlluence  of  certain  variations  in  the  state 
of  the  atmosj)liere. 

The  circumstances  that  accompany,  as  well  as  those  that  favor 
the  production  of  the  phenomenon,  demonstrate  that  it  must  be 
attributed  to  the  transmission  of  atmospheric  electricity.  This 
transmission,  in  fact,  does  not  <}ccur  in  a  continuous  manner, 
like  that  of  a  current,  but  rather  by  a  series  of  discharges.  Now, 
Mr.  Beatson  lias  demonstrated  that  the  ilischarge  of  a  Leyden 
jar  through  an  iron  wire  causes  this  wire  to  produce  a  sound, 
provided  i:  does  not  occur  too  suddenly,  but  is  a  little  retarded 
by  passaj/e  llirough  a  moist  conductor,  such  as  a  wet  string. 

The  sounds  given  out  by  iron  wire  and  by  magnetic  bodies, 
under  the  circumstances  that  we  have  been  describing,  seem  to  in- 
dicate, in  an  evident  manner,  that  magnetism  produced  by  the  in- 
fluence of  an  exterior  current,  as  well  as  by  the  direct  transmis- 
sion of  a  current,  determines  in  them  a  niodirication  in  the  ar- 
rangement of  their  particles,  that  is  to  sa\',  in  their  molecular 
constitution.  This  modification  ceases  and  is  constantly  pro- 
duced again  by  the  efTect  of  the  discontinuity  of  the  current; 
whence  results  the  pi-oduction  of  a  series  of  vibrations,  and  con- 
sequently different  sounds. 

A  gi'eat  number  of  observations,  made  by  different  philoso- 
phers, have  in  fact  demonstrated  in  a  direct  manner  the  influence 


JOULKS   EXI'KUIMKN'I-S. 


128 


of    iiiftgnetizati(jn  u[)on   tlio  luoloculiir  properties  of    maf^netic 
bodies.     M.  de  Wertlicim,  in  an  extensive  work  on  tlie  elasticity 
of  nietiils,  liiul  iilri'ady  observed,  tliat  niaf,Mi('ti/cation  produced  by 
means  of  a  helix  wliose  wire  is  traversed  liy  tbt;  electric  current 
produces  a  ditninution  in  tbe  eoeflicient  of  elasticity  in  iron  wire 
and  even  in  steel;  a  diminutio!i  wliicli,  in  tlie  latter  at  least,  re- 
mains in   part  even  after  tlie  interruption  of  llio  current     .\[.  ! 
Guilleniin  has  also  remarked  moic  recently,  that  a  bar  of  soft  ( 
iron,  fixed  i)y  one  of  its  extremities  whilst  the  other  is  free,  and) 
■which,  instead  of  remaining  hori/ontid,  is  curved  by  thoeilect] 


of  its  own   weight,  or  by  that  of  a  small  ailditioiiid  weight,  im- 


mediately rai.-^es  itself,  when  the  current  is  made  to  pass  in  the  ^ 
wire  of  a  helix  with  which  it  is  surrounded,  wdiieli  helix  is  itself 
raised  up  with  the  bar,  all  the  movements  of  which  it  follows, , 
since  it  is  coiled  around  it     This  cxpcritncMit  possc.-ises  this  im- 
])ortant  feature.— it  shows  the  magnetization  determines  a  modi-  , 
fication  in  the  molecular  state  of  iron  ;  for  it  cannot  be  exiilained  I 
by  a  mechanical  action,  which  could  only  occur  if  the   helix   is 
independent  of  the  l)!ir.    , 

Furthermore,  an  Knglish  philosopher,  Mr.  .loule,  succeede'l  in 
determining  the  inlluence  that  magnetization  can  exercise  over 
the  dimensions  of  bodies.  By  placing  a  soft  iron  b;  r  in  a  well 
closed  tube,  filled  with  water  and  surmounted  by  a  caiiillary 
tube,  he  lir.st  satisfied  himself  that  this  bar  experienced  no  varia- 
tion of  volume  when  it  was  magnetized  ly  means  of  a  powerful 
electric  current,  which  traversed  all  the  coils  of  an  enveloping 
helix.  In  fact,  the  least  variation  of  volume  would  have  b(>eu 
detected  by  a  chang(!  of  the  level  of  the  water  in  tlu!  caiiillary 
tube;  now  not  the  .slightest  is  observed,  however  powerful  the 
magnetization  may  be.  'Phis  result  is  in  accordance  with  what 
M.  (ray-Iais.'Jae  had  discoverecl  by  other  methods,  and  with  what 
M.  Wertlicim  had  also  obtained  by  operating  very  nearly  in  the 
same  manner  as  Mr.  Joule.  But  if  the  total  volume  is  not 
altered,  it  is  not  the  same  for  the  relative  dimensions  of  the  bar, 
which,  under  the  influence  of  magnetization,  experiences  m 
increase  in  length  at  the  same  time  as  it  does  a  diminution  in 


124 


THE   SI'KAKING  TELEPHONE. 


diameter,  at  least  within  certain  limits.  It  was  hj  means  of  a 
very  delicate  apparatus,  similar  to  the  instrument  employed  in 
measuring  the  dilation  of  si^lids,  that  Mr.  Joule  discovered  that 
a  soft  iron  bar  experience,-!  a  decided  elongation,  whicli  is  about 
sTTTj^-u^th  of  its  total  length,  at  the  moment  when  the  current  by 
which  it  is  magnetized  i^  established,  and  a  shortening  at  the 
moment  when  it  is  interrupted.  The  shortening  is  less  than  the 
lengthening,  because  the  bar  always  ret^uns  a  certain  degree  of 
magnetism.     It  would  appear  that  the  lengthening  is  propor- 

1  tional,  in  a  given  bar,  to  the  square  of  the  intensity  of  the 
magnetism  that  is  developed  in  it.  When  W(^  make  use  of  iron 
wires  instead  of  bars,  it  may  hap])en  that  it  is  a  shortening,  ami 
not  a  lengthening,  that  is  obtained  at  the  moment  of  magnetiza- 
tion. This  change  in  the  nature  of  the  elTect  is  observed  wiien 
th(^  degree  of  tension  to  which  the  wire  is  subjected  exceeds  a 
certain  limit. 

Thus  an  iron  wire.  12.^  inches  in  length  by  tI-  inch  in  diameter, 
di.stinctly  lengthens  under  the  influence  of  the  nuignetistn,  so 
long  as  it  is  not  exi)oscd  to  a  greater  tension  than  772  lbs.  ;  Imt 
the  less  so.  however,  as  it  approaches  nearer  to  this  tension. 
Setting  out  fn^m  this  limit,  and  for  increasing  tensions,  which  in 
one  cxjieriment  W';r(!  carried  up  to  17i'i4:  lbs.,  the  wire  was  con- 
stantly seen  to  shorten  at  the  moniiMit  wlien  it  was  magnetized. 

j  Tension  exercises  no  influence  over  highly  tempered  steel;  so 
there  is  never  any  elongation,  but  merely  a  shortening,  which 

I    commences  when  the  force  of  the  current  e\c(;eds  that  which  is 

'    nccessai'v  to  magnetize  tiie  bar  to  saturation.    •* 

M.  Wertheim,  on  ins  part,  at  the  close  of  long  and  minute 
researches,  snc<;eeded  in  analyzing  the  mechanical  clTects  that 
are  manifested  in  magnetization,  lie  found  that,  when  an  iron 
bar  is  lixed  bv  one  ol  its  extivmities,  and  the  bob])in  is  so  ])!ai'(id 
that  its  axis  coincides  with  that  of  the  bar,  no  lateral  movement 
is  observed,  but  merely  a  very  small  elongation,  which  rarely 
excecMls  .(l()07'i'  inch.  This  elongation  is  the  gn-atcM-  as  the  bol)- 
biu  is  situated  nearer  to  th(^  free  exti'cmity  of  the  bar,  and  dim- 
inishes in  ]ir<ipoi'tion  as   it  ajiproat'hes  the  point  by  which   it  is 


WERTHEIM  S   RESEARCIIKS. 


126 


fixed.  When  tlic  bar  ceases  to  bo  witliin  tlie  axis  of  the  bol>l)iii, 
tlic  elongation  still  remains;  but  it  is  accompanied  bv  a  lateral 
movement  in  the  direction  of  the  radius  of  the  bobbin.  The 
T)obbiii  that  was  employed  by  M.  Wertheini  was  9.8-i  inches 
lim^-,  and  7  inches  in  interior  diameter;  gla.sses  of  a  magnifying 
powei-  of  about  20  diameters,  and  mntaining  two  steel  wins, 
were  used  to  measure  the  elongation  ami  the  lateral  displace- 
ment. This  displacement,  or,  what  comes  to  the  same  thing,  the 
versed  sine  of  the  curvatun^  of  the  bar,  measui'cd  at  its  <'xtrcniity, 
was  determined  for  different  intensities  of  current;  and  it  ap- 
peared that  it  was  in  general  ])roportional  to  this  intensity,  but 
it  A'aried  foi-  each  position  of  the  bar  in  the  interior  of  the  bob- 
bin. However  it  may  be,  we  are  able  to  lind  for  each  of  the.se 
jiositions  the  mechanical  equivalent  of  the  unit  of  the  intensity 
of  the  I'urrcnt,  namely,  the  weight  which,  when  apjilied  at  the 
extremity  of  the  bar,  would  produce  the  .same  versed  sine. 
Thus,  for  example,  by  calling  the  length  of  the  part  of  the 
'radius,  comprised  between  the  axis  of  the  bar  and  the  axis  of 
the  bobbin  D,  the  vcM'sed  h\uv,  of  tlu^  curve  /,'  the  w(;ight  that 
would  ])roducii  tlu!  .same  ver.sed  sine  P,  the  following  results 
have  been  obtainc<l  by  attting  successively  upon  three  bars  of 
iron,  the  respective  masses  of  which  were  100,  40.5,  and  25.5 : 


No,   tiV  IIAKS. 


mil  J)— M). 


r.,n  ]>— ."ill. 


1,           

./■ 

.•i;th>i  fwi. 
.■t.itti;)a    " 

1,5-J4U     " 

1                 J' 
;     n^.'.i'i  irrw. 
'     41. 'Ji! 
!     Ii2.r>7 

1 

Tr. 

1 

/ 

.■J.'i^'i  fcut. 
l,.Vi::i     •' 

.y.'itiu    " 

r 

.W.Ml  jirs. 

•2:1.04 

1-2.55 

Tr. 

•> 

3 

We  calculate  P  from  the  formula  P.      l^'L^  C,  in  which  /'is  the 

versed  sine  of  the  curvature,  g  the  coeflicient  of  elasticity,  which 
is  27,122,653  Ib.s.  avoinlupois  perscpiare  inch  for  soft  iron,  i  and 
c  tlu!  width  and  thiekne.s.s  of  the  bar,  and  L  its  length  from  it8 
lixcd  point  to  its  free  extremity.  From  the  j)receding  table  we 
deduce  the  value  of  the   mechanical   forct's   that  are  between 


126 


THE   SPEAKING   TELEPHOXE. 


tliem  :  iov  D=80,  as  100  :  41.71  :  22.81 :  find  for  D=50,  as  100  : 
40.50  :  23.34.  So  we  may  conclude,  since  the  musses  of  the 
tliree  bars  are  together  as  100  :  40.5  :  25.5,  tliat  the  elfcct,  which 
is  here  an  attraction,  is  jtroportional  to  the  mass  of  iron  u[)ou 
whidi  tlie  curnnit  is  actinjj-.  We.  in  like  manner,  lind  that  it  is 
proportional  to  the  intensity  of  the  current;  which  would  render 
it  an  easy  manner  to  construct  upon  tliis  principle  a  \  ■^ry  sensible 
galvanometer,  by  employing  a  prismatic  b  'ibi.  .da  wide 
and  thin  iron  band. 

Thus,  all  the  experiments  that  we  have  been  relating  lead  us 
to  recognize  that  there  is  produced,  by  the  effect  of  magnetiza- 
tion, a  mechanical  traction,  due  to  a  longitudinal  component  and 
to  a  transverse  component:  that  tiic  latter  becomes  null  when 
the  l)ar  is  situated  in  the  centre  of  the  helix ;  that  they  are  both 
in-oportional  to  the  intensity  of  the  current  and  to  the  mass  of 
the  iron. 

It  is  a  more  difficult  matter  to  verify  the  elfeet  of  the  trans- 
mitted current  than  that  of  the  cxtei'ior  current,  by  which  nuig- 
nctizaiion  is  producecl.  In  fact,  in  tiie  former  ca.se,  the  mechan- 
ical effect  of  the  current  is  very  dillicultly  separated  from  its 
calorific  effect.  However,  it  follows,  from  auxnv  of  Mr.  Beatsnu's 
experiments,  that  an  inm  win^,  at  the  instant  it  is  jmt  int  ihi. 
circuit,  ajtpears  to  undergo  a  small  sudden  expansion,  an. 
very  distinct  from  the  dilatation  that  results  in  it,  as  Ut  ..".cr 
metals,  from  the  heating  produced  by  the  passage  of  the  curren, 

These  mechanical  effects  being  once  well  studii'd,  we  can  re- 
turn, with  greater  knowledge  of  the  cause,  to  the  study  itself  of 
the  sounds  that  accompany  !.>oth  magnetization  and  the  trans- 
mission of  currents. 

M.  Wcrtlieim  has  in  a  ])erfectly  accuiate  manner  vcrilied  the 
oxistence  of  a  longitudinal  sound  in  an  iron  or  .steel  bar  when 
jilai'cil  in  the  centre  of  helices  traversed  by  discontinuous  cur- 
rents. This  sound,  which  is  similar  to  that  produced  I' ;  ■  iction, 
is  due,  as  is  proved  by  direct  experiment,  to  vibration-  ;■  uaUy 
made  in  the  direction  of  the  axis.  AVith  wires  sub.stiti.te  i  for 
bars   the   effects  are  the  same,  except  that,  when   the  tension 


WKKTHEIM  S   KESEARCUES. 


127 


diminishes,  wc  hear,  in  addition  to  the  longitudinal  sound,  a  very 
j)eculiai'  metallic  noise,  wliicii  sccuis  to  run  along  the  wire,  as 
well  as  other  peculiar  noises.  Witli  transmitted  currents  we  also 
hear  tlus  longitudinal  .^^ound;  and  it  remains  nearly  the  same  in 
intensity  whether  the  current  traver.-<es  only  a  part  of  the  bar,  or 
traverses  the  whole;  a  jn'oof  of  the  analogy  existing  between  the 
iietion  of  the  transmitted  curnMit  and  that  of  any  t)ther  mechani- 
<'al  force,  such  as  friction:  e(iually  a  j)roof  that  the  s(jund  is  not 
due  to  vibrations  of  a  particular  kind,  engendered  l)y  the  current. 
The  longitudinal  sound  occurs  eipuilly  in  bars  and  in  wires;  but 
wluMi  we  operate  with  wires,  if  tluy  an;  not  well  stretched,  the 
longitudinal  sound  is  aecompanieil  by  tlie  divers  noi.ses  of  which 
we  have  spoken.  In  line,  whether  with  bars  or  wire.^i.  every  time 
the  current  is  transmitted,  but  only  in  the;  parts  where  it  passes, 
we  hear  a  dry  noise,  ii  crepitation  similar  to  that  of  the  spark, 
and  which  is  transformed  into  a  distinct  sound  oidy  iu  the 
stretcheil  ])ortion,  if  it  is  a  wire  that  is  in  the  circuit  Such  are 
the  facts  established  by  ^[.  Wertheim's  researches:  they  arc  of  a 
nature  to  eoiilirm  the  deiluetion  1  had  drawn  before  him  from 
the  sinipK'  study  of  the  sonorous  phenomena,  namely,  that  mag- 
netization on  the  pas,sigeof  the  electric;  cun-ent  produces  a  mole- 
cular derangement  in  magnetic  bodies,  and  that  the  sounds  arise 
from  the  oscillations  thatare  e\|)eri(Mieed  by  the  particlesof  bodies 
around  their  position  of  e(piilil)i'ium,  under  the  influence  of  cur- 
rents, whether  exterior  or  transmitted.  But  what  now  is  the 
nature  of  this  molecular  derangement?  and  how  is  it  able  to 
determine  both  the  mechanical  elTeets  and  the  sonorous  effects 
that  we  have  described?  When  the  action  of  exterior  currents 
is  in  f[uestion  we  may  form  a  tolerably  exact  idea  of  the  nature 
of  tin;  molecular  derangement  brought  about  by  magnetization. 
For  this  purpose  we  have  merc^ly  to  refer  back  U)  the  ex()eri- 
ment  iu  which  either  fragments  of  wire  or  iron  lilings  are  ])laced 
in  the  interior  of  a  helix  whose  axis  is  vertical.  As  soon  as  the 
current  is  made  to  ])a.ss  through  the  wire  of  this  helix  the  frag- 
ments of  iron  win>  all  ]>lace  themselves  ])arallel  to  the  axis,  that 
is  to  say,  vertieally,  and  the  fdings  Urrange  themselves  iu  small 


128 


THE   Sl'KAKING   TELEPHONE. 


clonpratpd  pyramids  in  the  diroction  of  tlip  axif,  which  destroy 
themselves  ami  rapidly  I'oriu  a,iraiii  wlieu  tiie  current  is  interniit- 
teiit.  The  action  of  tlie  helix,  therefore,  u\ym  filings,  consists  in 
grouping  them  under  the  forms  of  lilaments  j)arallel  to  the  axis — 
iihunents  which  gravity  alone  prevents  being  as  long  as  the  helix 
itself.  This  exiieriment  succeeds  equally  well  with  inipal[ial)le 
])0\vder  of  iron  as  with  tilings;  it  succeeds  erpially  well  with 
powder  of  nickel  and  cobalt;  only  if  the  current  that  traverses 
the  helix  is  discontinuous,  very  diirerentefTects  are  observed  witli 
each  of  these  thn>e  metals — effects  that  depend,  as  to  their  ]iar- 
tieular  nature,  upon  the  greater  or  less  numl)er  of  interrujitions 
which  the  current  experiences  in  a  given  time.  The  pyramids 
of  filings  are  at  their  maximum  of  height  wlieii  the  disk  that  sus- 
tains them  is  in  the  middle  of  thi'  helix.  They  turn  under  the 
iidluence  of  discontinuous  currents,  jiroviding  the  succession  of 
>^hese  currents  is  not  too  rapid,  so  that  there  are  not  more  than 
60  or  80  in  a  second.  With  100  there  is  no  longer  any  eiVeet. 
The.sc  difl'erences  are  imlircctlv  due  to  the  fact  that  the  softest 
iron  lias  still  some  coercitive  force,  and  that  it  requires  a  certain 
tinu!  for  magnetizing  and  demagnetizing.  By  comparing  under 
this  relation  iron,  nickel  and  cobalt,  all  reduced  to  an  impalj)able 
powder,  and  prepared  by  hydrogen,  we  lind  that  nickel  still  mani- 
fests movements  for  a  velocity  of  succession  of  currents,  at  which 
iron  ceases  to  manifest  any;  and  that  cobalt,  on  the  contrary, 
ceases  to  manifest  them  before  iron,  which  is  quite  iri  accordaiiee 
with  what  we  know  of  the  co(M'citive  force  of  these  three  metals. 
The  following  is  an  experiment  of  Mr.  Groves,  which  demon- 
strates in  an  elegant  manner  this  tendency  of  the  ])artieles  of 
magnetic  bodies  to  group  tlu'iiiselve.s,  under  the  influence  of 
magnetization,  in  a  longitudinal  or  axial  direction.  A  glass 
tube,  closed  at  its  two  extremities  by  glass  ])lates,  is  filled  with 
■water  holding  in  suspension  line  jiowder  of  a  magnetic  oxide  of 
iron.  On  looking  at  distant  objects  llirough  this  tube,  we  per- 
ceive that  a  considerable  ])roportioii  of  the  light  is  intermitted 
by  the  irregular  dis.seiiiination  of  the  solid  particles  in  the  water. 
But,  as  soon  as  an  electric  current  traverses  the  wire  of  a  helix, 


GROVE  S   EXPERIMENTS. 


12i> 


-with  which  the  tube  is  suiToiindcd,  tlic  particles  of  oxide  arrange 
themselves  in  a  regular  nml  syminetrical  iiiauner,  so  as  to  allow 
the  larger  jjroportion  of  tiie  light  to  pass.  The  particles  in  this 
case  are  not  small  fragments  of  iron  wire,  art i Ilea  11  y  disaggre- 
gated from  a  more  cimsidcrabh^  mass,  but  iron  precipitated 
chemically,  and  conseciucntlv  in  its  natural  molecular  .state,  such 
as  constitutes  a  solid  bodv  bv  its  aggregation. 

This  dis])osition  of  the  particles  of  iron  and  of  magnetic 
bodies  to  approach  each  other  in  the  transvei'se  direction,  and  to 
extend  in  the  longitudinal  diri-ction,  under  the  influence  of 
an  exterior  magnetization,  which  is  probaldy  due  to  the  form 
of  tlie  element  irv  molecules,  and  to  the  manner  in  which  they 
are  polari/.ed,  is  now  estal)lislie(l  in  an  irrefragable  manner  by 
direct  and  jiurely  mechanical  ])ro(ifs. 

It  is  easy  to  see  that  it  accounts  in  the  clearest  manner  for  the 
production  of  sound  in  a  bur  or  a  wire  sul)jectcd  to  the  influence 
of  the  intermittent  cui'rcnt  of  the  helix.  The  jinrticdes  contend- 
ing against  cohesion  arrange  themselves  in  the  longitudinal 
direction  when  the  current  acts,  and  return  to  their  primitive 
position  as  soon  as  it  ceases:  thert;  follows  from  this  a  .'<eries  of 
oscillations,  which  are  isochronous  with  the  intermittence  of  the 
current.  .\11  tlise  cfTects  arc  much  more  decided  in  soft  iron 
than  in  .steel  or  hardened  iron.  l)ccau.se  the  particles  of  s(jft  iron 
are  much  more  mobile  around  tluMr  position  of  equilibrium. 

I  have  also  remarked  that  both  iron  and  steel,  when  they  arc 
already  magnetized  in  a  jiermancnt  manner  by  the  current  tnins- 
mitted  through  a  second  helix,  or  by  the  action  of  an  ordinary 
magnet,  do  not  experience  such  stronii  vibrations  when  the  <Iis- 
continuous  current  tends  to  magneti/.e  them  in  the  directi(»n  in 
which  they  are  already  magnetized,  but  stronger  ones  in  the 
contrary  ca.'<e.  It  is  evident  that,  in  the  former  case,  the  par- 
ticles already  ])o.ssess,  in  very  nearly  a  permanent  manner,  the 
position  that  the  exterior  action  to  which  they  are  submitted 
tends  to  impress  upon  them;  while,  in  the;  latter  case,  they  are 
farther  removed  froni  it  than  they  are  in  their  natural  jjosition. 
Much  mure  powerful  oscillations,  therefore,  ought  to  occur  to 


130 


THE   SPEAKING  TELEPHONE. 


them  around  their  position  of  cqnilil)rium  in  the  latter  case,  and 
less  ]in\verfiil  in  the  former,  than  wlien  they  arc  in  tlieir  normal 
position,  at  the  moment  when  the  <li.srontinuous  current  exer- 
cises its  action. 

The  effects  of  the  transmitted  current  arc  due  to  an  action 
of  the  same  order,  hut  acting  m  a  different  direction.  In 
order  to  analyze  tliis  action  well,  w^e  must  study  the  (Hstri- 
bution  of  iron  lilings  around  a  wire  of  iron,  or  of  ;iny 
other  metal  traversed  hy  a  powerful  electric  current.  '^I'licse 
filings  always  place  themselves  so  as  to  form  lines  ])erpendicu]ar 
to  the  direction  of  the  current,  and  consei[u»'ntly  ])arallel  to  each 
other  This  is  very  readily  jierccived  l)y  lixing  the  conducting 
wire  in  a  groove  formed  in  a  wooden  jilank,  co\ered  with  a  sheet 
of  pajier  wyion  which  the  fdings  are  ])laeed.  The  latter  arrange 
themselves  transversely  ahove  the  wire,  whatever  he  the  manner 
in  which  it  is  curved,  fomiing  small  fdaments  of  the  sixtii  or 
eighth  of  an  inch  in  length,  which  presenc  o])posite  jioles  at  tluMr 
two  extremities^.  When  the  conducting  wire  is  frct>,  these  liht- 
ments,  instead  of  remaining  rectilinear,  join  together  hy  their  two 
edges,  and  envelop  the  sin-face  of  the  wire,  forming  around  it  a 
cloi^cd  curve,  like  a  s))eeies  of  envelope  composed  of  rings  that 
cover  each  other  and  are  jiressed  against  each  other.  Now,  the 
arrangement  assumed  hy  the  particles  of  iron  tilings  round  any 
conducting  wire,  iron  as  well  as  every  other  metal,  when  it  trans- 
mits a  cuiTcnt,  ought  to  he  in  like  manner  assunicd  hy  the  mole- 
cules of  the  very  surface  of  a  soft  iron  v»'ire  itself  traversed  by  a 
current,  under  the  influence  of  the  current  transmitted  by  the  en- 
tire mass  of  the  wire.  This,  also,  is  equally  demonstrated  by  the 
mechanical  effects  studied  by  Joule  and  Beatson,  It  follow.s, 
therefore,  that  when  the  transmitted  current  is  intermittent  the 
particles  of  the  surface  of  the  iron  wire  oscillate  between  the 
transverse  position  and  their  natural  position,  and  that  there  is 
consequentlv.  a  production  of  vibration.s.  These  oscillations 
ought  to  be  the  more  easy,  and  consequently  the  vilirations 
more  pow(M'ful,  as  the  iron  is  .softer;  with  hardened  iron,  and 
especially  with  steel,  there  is  a  greater  resistance  to  be  overcome ; 


DK    LA   KIVKS   HKSEAKCIIES. 


131 


thus  the  offcft  is  loss  sensible.  If  tlic  wire  thnt  transmits  the 
(liscoiiliiuiouri  current  is  itself  traversed  hy  a  continuous  current 
moving  in  the  same  direction  as  the  discontinuous  one,  the  oscil- 
latory movement  oudit  to  In-  auuuUeil,  or  at  least  notably  di- 
minished, since  the  trausmissiou  of  the  continuous  current  im- 
])rcsses  npon  the  ])articles  in  a  ])enuancnt  manner  the  ])Ositiou 
which  the  passage  of  the  discontinuous  current  tends  to  give  them 
in  a  temporary  maTiner.  Thus  the  sound  in  this  ease  would  com- 
])letely  disa])])ear  or  notablv  dimiuisli.  If  the  wuv.  is  of  steel  or 
of  well  hardened  iron,  the  continuous  current  is,  on  the  contrary, 
favorable,  by  its  presence,  to  the  oscillating  action  of  the  discon- 
tinuous current,  because  it  deranges  the  particles  from  their  nor- 
mal position,  without,  however,  being  able  couipletcly  to  im])ress 
ujion  tiiem  the  transverse  direction,  on  account  of  the  too  great 
resistance  they  op})ose  to  a  displacement,  which  is  easily  brought 
about  in  soft  iron.  The  two  currents  united  pro<luce  what  a 
single  current  would  not  be  able  to  accomplish,  or  would  accom- 
plish less  cllcctually,  and  the  sound  is  then  reinforced,  as  is  j)roved 
by  cx])eriinent  In  sup])ort  of  the  explanation  that  Ihave  just 
given,  I  have  found  that  a  cop])er  wire,  with  a  thin  enveh)pe  of 
iron  which  is  contiguous  to  it,  gives  rise  to  the  same  effects  and  of 
lu'arly  the  same  intensity,  wheu  the  discontinuous  current  tra- 
verses it  as  if  it  were  entirely  of  iron  :  the  sound  is  merely  less 
musical;  it  resembles  that  which  M.  Wertheim  designated  under 
the  name  of  "metallic;'"  (iron-y  /era/YA).  As  this  result  might 
be  attributed  to  a  part  of  the  current  traversing  the  iron  envelope 
it.'olf,  instead  of  circulating  exclusively  through  the  copper  wire, 
I  insulated  the  latter  by  means  of  a  thin  covering  of  silk  or  wax, 
so  that  the  iron  cylinder  that  surrounds  it  is  not  able  to  com- 
municate metallically  with  the  copper.  The  effect  is  exactly  the 
same  as  in  the  preceding  case,  that  is  to  say,  the  discontinuous 
current  that  tra\erses  the  copper  wire  determines  a  series  of  vi- 
brations in  the  iron  cnvelojie,  which  ])rovos  that  we  may  admit 
that  the  same  elfect  is  produceil  U[)on  the  surface  of  an  iron  wire 
which  itself  transmits  the  current.  With  regard  to  the  euvelo])e, 
we  can  easily  i)rove  that  it  expei'iences  a  transverse  magueti- 


182 


THE   SPEAKING   TELEPHONE. 


zation  when  the  copper  wire  is  in  the  voltaic  circuit;  for  if  we 
make  in  it  a  small  loiigitudiiial  groov(>,  \vc  perceive  tliattlic  iron 
liliugri  arc  attracted  upon  its  two  edges,  which  have  also  an 
opi)Ositc  j)olarity. 

The  detailed  explanation  that  we  have  given  of  the  molecular 
])hcnoniena.  which,  in  magnetic  hodies,  aceoiiipany  the  action  of 
currents  both  exterior  as  well  as  interior,  llnds  a  further  con- 
firmation in  the  observMtion  of  several  facts  of  different  kinds. 
Thus  I  have  remarked  that  ]>ermanent  magnetization,  whether 
impressed  upon  a  soft  iron  rod  by  the  action  of  an  envclo[)ing 
helix,  or  by  the  action  of  a  jiowcrful  electro-magnet,  increases,  in 
a  very  decided  manner,  the  intensity  of  the  .sounds  that  are 
given  out  by  this  rod,  when  traversed  by  a  discontinuous  cur- 
rent. 

This  reinforcement  is,  in  fact,  evidently  due  to  the  conflict  that 
is  established  between  the  longitudinal  direction  that  is  impressed 
upon  the  particles  of  iron  by  the  influence  of  the  magnetization, 
and  tlie  transverse  direction  that  the  passage  of  the  current  t(Mids 
to  give  to  them.  The  oscilhitions  of  tlie  j)articles  ought  neces- 
sarily to  have  greater  amplitude,  since  they  occur  between  more 
extreme  positions.  The  effect  is  more  decided  with  .soft  iron 
rods  than  with  tiiosc  of  steel,  and  especially  tempered  steel. 
Mr.  Beatson  arriveil  at  a  similar  rcsiUt  by  quite  another  method. 
lie  observed,  that  if  a  continuous  current  tra\er.-;es  a  wire,  and 
if,  at  the  same  time  it  is  subjected  to  the  action  of  a  helix  in 
which  a  discontinuous  eurivnt  is  passing,  the  wire  will  undergo 
a  series  of  contractions  and  ex[)ansioiis  which  become  inappreci- 
able, if  the  continuous  current  ceases  to  be  transmitted,  even 
when  the  helix  continues  to  act  in  the  same  maimer.  The 
autlun'  drew  from  this  the  same  conclusion  that  I  had  deduced 
from  the  sonorous  effects,  namely,  that  the  action  of  the  helix 
impresses  ui)on  the  particles  of  iron  an  opposite  state  to  that 
which  is  produced  by  tlu;  transmitted  current,  and  that  one  of 
these  actions  has  the  tendency  to  invert  the  arrangement  which 
the  other  tends  to  establish. 

A  very  curious  fact  is  that  magnetization  tends  to  impress 


MAGGI.S  HEAT   EXI'KUIMKNTS. 


133 


upon  tlio  particles  of  soft  iron  an  arrangement  similar  to  that 
which  they  jtosscss  in  tempered  steel,  even  before  it  is  magnetized. 
What  conlirms  the  correctness  of  this  remark  is,  that  tlie  S(jund 
which  magnetized  soft  iron  gives  out  under  the  action  of  the 
transmitted  current,  is  not  only  more  powerful  than  it  is  when 
then;  is  no  magnetization,  l)\it,  it  also  acquires  a  peculiar  diy 
tone,  which  makes  it  resemble  that  which  steel  gives  out  with- 
out being  magnetized. 

The  very  remarkable  influence  of  tension,  which,  beyond  a 
certain  limit,  diminishes  in  soft  iron  wires  their  aptitude  to  give 
sounds,  is  a  further  consequence  of  our  explanation.  In  fact, 
the  molecules,  by  the  elTect  of  tension,  undergo  a  permanent 
derangement  in  their  normal  ])()sition,  and  are  consequently 
found  cripplcil  in  their  movements,  and  arc  no  longer  able, 
under  the  influence  of  exterior  or  interior  causes,  to  execute  the 
oscillatory  movi^ments,  and  consequently  the  vibrations  which 
constitute  the  >"und. 

Two  facts,  of  a  eliaractcr  altogether  different  from  the  })r(>ceil- 
ing,  still  further  show  that  the  magnetization  of  iron  is  always 
attended  by  a  molecular  change  in  its  mass. 

The  lirst  of  these  facts  was  discovered  by  Mr.  Grove.  It  is, 
that  an  armature  of  soft  iron  experiences  an  elevation  of  tem- 
perature of  several  degrees  when  it  is  magnetized  and  demaguet 
izcd  several  times  successively  by  means  of  an  electro-magnet,  or 
even  of  an  ordinary  magnet  set  in  rotation  in  front  of  it.  CobaU 
and  nickel  ])rescnt  the  same  phenomenon,  but  in  a  somewhat 
slighter  degnn; ;  whilst  non-magnetic  metals,  placed  under  exactly 
the  same  circumstances  do  not  ])resent  the  slightest  traces  of 
calorific  effects.  Tiiis  exjJerinuMit  can  only  In;  explained  by 
admitting  that  the  development  of  heat  arises  from  the  mole- 
cular changes  whicli  accompany  magnetization  and  demagneti- 
zation. The  sccoml  fact,  which  is  no  l(>ss  inq)ortant,  is  due  to 
Dr.  ^raggi.  of  ViM'ona,  who  ])rovcd  that  a  circular  ]ilate  of  very 
homogeneous  soft  iron  condu(>ts  heat  with  more  facility  in  one 
direction  tlian  in  the  other  when  it  is  niagn(-tize(l  by  a  powerful 
electro-magnet ;  whilst,  when  it  is  in  the  natural  state,  its  conduct- 


134 


TIIK   SPEAKING   TELEPHONE. 


ibilitv  is  tlic  same  in  all  directions,  and,  consequently,  jieHectly 
uuilnrni.  The  j)late  is  covered  with  a  tiiiii  coating'  of  wax  melted 
with  oil,  and  the  heat  arrives  at  its  centre  hy  a  tuhe  that  tra- 
verses it,  and  in  the  interior  of  which  the  vapor  of  hoiling 
water  is  i)assing.  Tin;  ])late  is  jilaet'd  horizontally  on  the  two 
poles  of  a  jiowerful  eleetro-ina^niet,  several  insulatiiijr  cards  jire- 
vcnting  contact  between  it  and  the  iron  of  tlie  electro-magnet. 
So  long  as  it  remains  in  its  natural  state,  the  curves  that  bound 
the  melted  wax  assume  the  circular  form  which  in<lieatcs  a  uni- 
form conductibility  for  heat  in  all  directions.  But,  as  soon  as 
the  clectroniagnet  is  magnetized,  the  curves  are  di'foruied;  and 
they  are  always  elongated  in  a  direction  perj)endicular  to  the 
line  that  joins  tlio  magnetic  poles ;  whicli  ])roves  that  the  con- 
ductibility is  better  in  the  direction  iierpeudicular  to  tho 
magnetic  axis  than  in  the  direction  of  the  axis;  a  result  in 
aceorchmce  with  the  fact  that  we  have  established,  that  the  i  ar- 
ticles of  iron  approach  each  other,  by  the  eOVct  of  magnetiza- 
tion, in  the  direction  ])crpendiciUHr  to  tlu^  length  of  the  magnet, 
and  recede  in  the  direction  of  that  length,  which  is  always  the 
magnetic  axis. 

INFU'ENCE    OF    jrOLECTLAR     ACTTONS    L'PON    MAGNETISM 
PKODL'CEI)   nv   DYNAMIC   ELECTHICITY^ 


We  have  seen  that  heat,  tension,  and  mechanical  actions  gen- 
erally facilitate  magnetization,  i  M.  Matteucci  has  found  that 
torsion  and  percussive  and  mechanical  actions,  not  only  facilitate 
the  magnetization  produced  uj)on  soft  iron  by  a  helix  that  is 
traversed  by  a  powerful  current,  but  they  also  contribute,  when 
the  current  has  ceased  to  pass,  to  the  destruction  of  magnetism 
in  a  very  rapid  manner.  The  same  ]ihiloso])her  has  likewise 
observed,  that  torsion,  when  it  docs  not  ]xiss  beyond  certain 
limits,  augmented  tho  magnetization  produced  upon  steel 
needles  by  disehaiges  of  the  Leyden  jar. 


*  M.  LiigcrliJL'liii  obrtLTVcd  tliiit  iron  bucoiuos  strongly  iimgiiutic  by  riiiiturc. 


MAKIANIXI  A  EXI'KKIMKNTS. 


185 


M.  Marianini,  who  lias  inadii  iiiiincrDiis  and  interesting  re- 
seurclies  u[)()ii  luagiicti/.atioii,  arrivtMl  at  curious  results  upon 
tlio  iiptitudo  that  iron  bars  may  ac([uii'(3  (jf  heconiing  more 
easily  maffiietized  in  one  direction  tliaii  in  another,  and  even  in 
being  little  or  much  magncti/,c(l  by  the  influence  of  the  same 
euusc.  When  an  iron  bar  has  ])een  magnetized  })y  the  inlluence 
of  un  instantaneous  cuiTcnt  that  circulates  around  it,  and  when 
it  lias  lost  this  magnetization  l.iy  the  action  of  a  contrary  cur- 
rent, it  i3  more  ai)t  to  l)e  magnetized  afresh  in  the  former  case 
than  in  the  latter.  "We  are  able,  by  contrary  currents,  to  give  it 
even  more  aptitude  to  bo  magnetized  in  the  latter  direction  than 
in  the  ft)riuer.  The  augmentation  of  a[)titude  that  it  acquires 
of  being  magnetized  in  one  direction  is  equal  to  the  loss  of  apti- 
tude that  it  exj)erienccs  for  being  magnetizc(l  in  the  other  direc- 
tion. Rut,  by  reiterating  the  action  of  the  currents  upon  the 
same  bar,  the  increase  of  aptitude  in  oik;  direction,  and  the  cor- 
responding diminution  in  the  other,  bc(;ome  always  more  and 
more  feeble.  The  modilications  of  aptitude;  for  acquiring  mag- 
netization are  accouipaiiied  l)y  modilications  in  the  aptitude  for 
losing  this  magnetization  ;  but  in  such  direction  that  the  latter  is 
the  I'cverso  of  the  former. 

Willing  t<j  enter  more  deeply  into  the  study  of  the  effects 
that  we  have  been  I'clating.  M.  Marianini  sul)jected  iron  to  differ- 
ent ])hysical  and  mechanical  actions.  First  of  all,  lie  satisfied 
himself  that  neither  elevation  of  temperature,  nor  cs[)ecially  the 
cooling  by  whicli  it  is  followed,  neither  percussion  nor  torsion, 
n(jr  a  violent  shock,  nor  any  me(,-hauical  a(*'oii,  even  the  most 
energetic,  are  able  of  themselves  to  determine  magnetization: 
nor,  indeed,  does  the  discharge  of  a  Lcyden  jar  through  an  iron 
bar  magnetize  it.  But  the.se  various  operators,  incapable  of 
magnetizing,  may  all  scr\'e  to  destn)y  the  ]iolarity  of  magnetized 
bodies  ;  the  quantity  of  magnetic  force  that  they  thus  lose,  when 
their  aptitude  has  not  been  altered,  is  tli(»  greater,  as  the  magnet- 
ization has  been  more  feclile.  But  if.  after  ha\-ing  undergone 
one  of  these  actions,  the  bar  has  still  i)rescrved  a  little  magnet- 
ism, it  can  no  longer  lose  it  by  this  or  liy  any  similar  action. 


136 


THE   SPKAKINO   TELEPHONE, 


What  irt  very  remarkable;  is,  that  when  tlio  magnetism  of  a  bar 
lias  been  destroyed,  on  remagnctiziiig  it  in  a  roiitrary  direction 
by  a  succession  of  instantaneous  curnMits,  so  that  its  lua^nictiza- 
tion  is  null,  we  may  restore  to  it  its  former  magnetism  by  means 
of  a  violent  shock,  by  lotting  it  fall,  for  instanee,  on  the  pave- 
ment from  the  height  of  a  conplo  of  yards.  The  greater  the 
height  of  the  fall,  the  more  powt>rfnl  is  the  magnetism  it  re- 
covers.  Thus,  a  bar,  that  made  a  needle  deviate  00^,  having 
been  brought  by  a  sueeession  of  discharges  to  exercise  no  devia- 
tion beyond  0°,  gave  li°  on  falling  from  a  height  of  12.8  feet, 
15°  SO'on  falling  from  a  height  of  lo.O  feet,  a  '  21'  on  falling 
from  a  height  of  (i.l  feet*     This  new  polarit  in  the  same 

direction  a.s  the  primitive  one. 

Even  when,  by  destroying  the  primitive  magnetization  of  the 
bar,  we  have  actually  imparted  to  it  a  new  one  in  a  contrary  di- 
rection, we  lind  on  letting  it  fall  npoii  the  ])avement  that  we  re- 
.'^tore  to  it  thelirst  that  is  jiossessed.  ^I.  Marianini  would  be  dis- 
])oS(>d  to  believe  from  this  expiu'iment  and  other  similar  ones,  that 
the  bar  had  retained  its  fonner  magnetization  while  still  acquir- 
ing the  contrary  one,  which  ncntralizcMl  the  elT(>ct,  of  the  Iirst  and 
even  surpasses  I  it ;  and  the  shock  merelv  dcstnivcd  the  second, 
either  in  whole  or  in  part,  which  ])ci'niittcd  the  former  to  reap- 
pear. Fle.xion,  friction,  heat,  or  an  electric  discharge  traversing 
the  iron  directly,  niay  take  the  place  of  the  shock,  particularly 
when  very  line  wires  are  iiMjuestion. 

The  action  that  is  exercised  by  an  instantaneons  discharge 
through  the  wire  of  a  helix  iipon  a  body  already  magnetized,  in- 
creases or  diminishes  the  magnetism  of  this  body  according  to  the 
direction  in  which  it  is  sent ;  but  this  increase  oi-  diniiimtioii  isthe 
less  sensible  as  tlit;  iron  is  more  magnetized.  In  any  case,  a 
given  instantaneous  current  produces  ]iroporti()natcly  more  elleet 
when  it  is  maile  to  act  with  a  view  of  diminishing  the  polarity  in 
the  magnetized  bodies  than  when  it  is  made  to  act  with  a  view  of 
increasing  it. 

M.  .Marianini,  in  order  to  ex])laiu  the  results  of  these  experi- 
ments, admits  a  dillerence  between  what  he  calls  polarity  and 


MAUIAMM  S    KXI'KUIMRNTH. 


187 


magnotism.  Thus,  the  sumo  Jii;i<(iM't,  ulthoiigli  doprivcil  of 
polarity,  may  very  readily  ivUiiumagiiolisin,  wlieii  magiit'tixcd  ut 
one  time  in  two  contrary  directions  with  iiii  equal  force.  Wo 
must  tli(>n  su|)|)f)so  that  contrary  magnetic;  systems  ])rodueing 
e((uilil)rium  are  able  to  exist  in  iron,  and  that  exterior  forces, 
such  as  a  current  or  o,  nieehanieal  action,  do  not  act  with  the  same 
energy  u))on  tlio  o])|)()sito  systems.  This  opinion,  which  doea 
not  as  yet  appear  to  us  to  rest  upon  facts  sullieiently  numerous, 
has,  however,  nothing  in  it  that  is  inadmissil)le  ;  nothing,  in  fact, 
oj)poses  there  being  in  thesamo  liar  a  certain  numlierof  ij.article.s 
arrange(l  so  as  to  produce  a  m;  uiietization  in  a  certain  direction, 
and  others  so  as  to  prcMluce  magnetization  in  the  op{)osite  di- 
rection ;  as,  for  example,  the  interior  particles  m.'iy  l)e  found  to 
liavo  in  this  r(>spect  an  arrangement  the  op|)osito  of  those  on  the 
surfaces;  and  that  such  exterior  action  operates  proportionately 
with  greater  force  nj)on  the  one  than  upon  the  other.  This 
jKjint  Would  need  to  be  made  clear  by  further  observations,  and 
especially  by  comparative  ex[)eriinents  made  upon  bars  of  dif- 
ferent forms  and  different  dimensions — upon  liollow  and  solid 
cylinders,  forexamjile.  Rut  if  some  doubts  still  remain  upon 
the  conclusions  that  M.  Marianini  has  drawn  from  iiis  experi- 
ments, there  are  not  any  iijion  the  new  proof  which  they  liring  in 
favor  of  the  connection  that  exists  between  magnetic  and  mole- 
cular phenomena.  Tlic(bfTerent  degrees  of  ai)titudeae(piired  by 
iron  under  the  influence  of  certain  actions,  of  becoming  more  easily 
magneti/,cd  in  one  direction  tlian  in  thoother,  arealNiuite  in  har- 
mony with  tlio  disposition  with  which  the  [)articles  of  Ixxhes  are 
endoW(>d  toari'angc;  themselves  more  easily  in  one  direction  than  in 
another.  'I'his  los.s  of  ajititude,  after  the  multiplied  repetition  of 
the  contrary  actions,  corresponds  with  the  inditlerenee  to  arrange 
themselves  in  one  manner  or  the  other,  which  is  fin.ally  presented 
by  the  j)articles  of  bodies,  aft(>r  having  experienced  numerous 
dcranw'nients  in  different  directions,  i     Finallv  the  RMuarkable 


iWi'  liiivu  II  rcniiirkiil)li'.  cxiiinplu  of  tliU  in  tlu^  frii/ility  |)rcs('iit('il  by  iron  wlieii  it 
has  lici'ii  for  II  loii|^  tiiiio  HuliJL-ctfJ  to  riipid  mid  I'lvciuuia  viliriitious,  us  arc  tlir  axles 
(if  loc'oiucitivus. 


138 


THE   SPEAKING  TELEPHONE. 


effects  of  shock,  flexion,  heat,  in  fact,  of  all  tliosc  actions  that 
change  tlie  relative  position  of  the  particles,  ctviiie  in  supjiort  of 
the  relation  tliat  we  liav(!  endeavored  to  establish. 

Tlic  whole  of  the  nuigneto-molecular  phenomena  that  we  have 
been  studying,  lead  us  t( >  believe  that  the  magnetization  of  a 
body  is  due  to  a  ]iartieular  arrangement  of  its  molecules,  origin- 
ally endowed  with  magnetic  virtue;  Init  whicli,  in  the  natural 
state,  are  so  arranged,  that  the  magnetism  of  the  body  that  they 
constitute  is  not  a])])ai'ent.  Magnetization  would  therefore  con- 
sist in  disturl)ing  tliis  state  of  e(|uilil)rium,  or  in  giving  to  the  par- 
ticles an  arrangement  that  malce.;  manifest  the  prop('rt3'  with  which 
they  are  endowed,  and  not  in  devcIo])iugit  in  tiieni.  The  coerci- 
tivc  force  would  be  the  resistance  of  the  molecules  to  change 
their  relative  i)ositii)iis.  ileat,  by  facihtating  the  movenwnt  of 
tlic  particles  in  respect  to  each  otiier,  diminishes,  as  indeed  does 
every  mechanical  action,  this  resistance,  that  is  to  say,  the  coerci- 
tive  force. 

I'here  remains  an  important  question  to  be  resolved.  Are 
mechanical  or  otlier  actions — ilisturl)ers,  as  they  are,  of  the  electri- 
cal state — al)le  of  tliem.selves  to  give  rise  to  magnetism?  or  do 
they  only  facilitate  the  action  <jf  an  extericjr  magnetizing  cau.se; 
for  example,  terrestrial  magnetism,  which,  in  the  al)sence  of  all 
others,  is  ever  ])resent?  M.  .Marianini's  researches  woidd  seem 
to  be  favorable  to  the  hitler  o[)inion;  liowever,  the  facts  tiiat  an; 
known  do  not  ajjpcar  to  us  sullicicnt  as  yet  to  e.stablisli  it  in  an 
incontestabl(!  manner.  Let  us  remark  that,  even  although  it 
should  1)0  estal)lishe(l.  yet  the  non-existence  of  a  previous  and 
proper  polarity  of  magnetic  bodies,  or  of  electric,  currents,  cireu- 
hiting  around  tliem  in  a  determinate  direction,  would  not  neees- 
.sirily  follow.  We  should  merely  conclude  from  it  that,  in  the 
al)seiice  of  an  exterior  acting  cause,  the  particles  when  left  to 
thcMisclves,  coiistautly  ai'range  tliem.selves  so  as  to  determine  an 
('(piilibrium  between  their  opposed  polarities;  whence  results  the 
nullity  of  all  exterior  action. 


TONES    PRODUCED   BY   ELECTRICITY. 


139 


A   NEW    METHOD    OF   PRODUCING    TONES    BY  THE    ELECTRIC 

CURRENT. 

1  In  1837  Dr.  Page,  of  Salem,  Mass.,  made  the  important  dis- 
covery that  a  lionst'shoe  magnet,  before  or  between  wlio.se  poles 
a  Hat  spiral  of  copper  wire  was  suspended,  began  to  emit  tones 
whenever  li(>  passed  through  the  spiral  the  discontinuous  current 
of  u  galvanic  battery. 

Other  physicists,  and  especially  Delezenne,  Beatson,  Marriau, 
Alatteucci,  Dc  la  Rive,  and  Wertheim,  in  Ibilowiiig  up  the  dis- 
covery, have  sliown  us  that  it  is  tlic  intcrrnptc<l  curnnit  oidy 
which  generates  this  new  formatiDU  of  tones,  and  that  for  this 
purpose  it  can  be  aj)plied  in  two  ways,  either  direct,  as  when  it  is 
pa.ssed  through  the  bodies  thcm.selve.s,  or  again,  when  conducted 
through  a  hclicul  wire  phiced  around  these  bodies. 

In  this  manner  tones  have  been  produced  in  iron  and  steel, 
and  in  these  metals  only  it  would  seem,  as  Wertheim  has  found 
from  iictuiil  experiment,  that  bars  and  wires  of  other  metals 
cannot  l)e  made  to  emit  tones  liy  eithei' method :  and  although 
-De  la  Eive  says  in  iiis  lii'st  treatise  that  he  has  obUiiucd  tones  by 
botli  methods  from  platinum,  silver,  co])per,  brass,  lead,  tin,  and 
zinc,  it  will  bt^  ol)sei'ved  that  he  modilies  this  assertion  in  a 
snl)seiiuent,  work  by  saying  that  this  took  phiro.  only  when  a 
])owerful  electro-magnet  was  acting  at  th(>  s:une  time  (^n  the  wire. 

Tilt!  method  wiiicli  we  ai'c  now  about  to  describe,  and  which 
the  writer  happened  to  discovei'  accidentally  in  the  fall  of  1854, 
possesses  the  advantage  of  generalizing  matters,  as  it  shows  that 
all  metals  can,  under  certain  onditions,  be  made  to  emit  tones; 
there  are  also  other  consid  -atious  which  render  it  interesting  as 
regards  its  connection  with  the  theory  of  electricity.  This 
method  is  based  u[)on  tlu^  intei'ruptions  of  a  battery  curnMit, 
although  ill  reality  it  is  not  the  latter,  but  rather  the  induced 
(/urrents  ]U'oduced  by  tlie  intci'ruptions  that  nnist  bo  considered 
as  the  generator  of  the  tones.      In  place  also  of  bars  or  wires  as 


1  .1.  C.  Pn(t)reiulorf.     I'i)if(,'i'udi)rf  8  .Viinuluii,  .Moviii.,  p.  l!»;i.    Mdimtsburichti'ii  dor 
Aoiul.     Miirz,  IKnii. 


140 


THE   SPEAKING   TELEPHONE. 


heretofore  used  for  producing  the  tones,  tuljes  formed  of  sheet 
metal  are  substituted,  and  surround  the  coils  through  which  the 
current  is  passed. 

The  writer  u.sed  in  his  experiments  coils  five  inches  in  length 
and  about  one  and  one  eighth  inches  in  diameter.  Both  wires 
of  the  coils  were  connected,  .so  tiiat  their  united  length  was 
about  100  feet;  the  diameter  of  the  wire  was  1.4  millimetres. 
The  coils  were  maintained  in  a  vertical  i)osition  by  means  of  a 
.^tand  provided  for  the  purpo.se,  and  so  ])luced  that  tlie  lower 
ends  could  be  connected  to  the  battciy,  which,  as  a  rule,  consisted 
simply  of  a  single  Grove  cell.  The  tubes  to  be  examined,  which 
were  about  five  inches  long  and  from  two  to  four  inches  in 
diameter,  wert'  then  [)laccd  over  the  coils.  Some  of  them  were 
left  entirely  o})en,  sonu;  closed  by  .soldering,  and  others  bent 
together  so  that  the  edges  just  touched  each  t)ther.  The  ma- 
terial of  the  tubes  consisted  of  platinum,  copper,  silver,  tin, 
brass,  zinc  lead  ami  iron. 

A  Wagcner  hammer  of  peculiar  construction,  so  as  to  dead(>n 
the  noise  of  its  own  vibrations,  and  thus  prevent  it  from  interfer- 
ing with  the  investigations,  was  u.-;e(l  fur  interrupting  the  current 

From  the  experiments  made  with  this  ajtjjaratus  it  has  been 
found  that  ikjiic  of  the  metals,  except  iron,  can  be  made  to  emit 
tones  when  formed  into  either  open  or  completely  closed  tubes 
and  placed  over  the  eoils.  If,  liowever,  th(>  edges  of  the  tubes 
just  touch  each  otliei',  then  all  metals  can  be  made  to  emit  a 
vcrv  auililile  lone,  whicli  will  vary  in  louilness  and  ipiality  of 
.-^ound  with  the  dimensions  of  the  tubes,  the  elasticity  and  qual- 
ity of  the  material  employed,  the  strength  of  the  current,  and 
certain  other  minor  considerations  that  will  readily  suggest 
themst'lve.'*. 

Iron  is  distinguished  from  the  other  metals  by  the  fact,  tlue 
no  iloubt  to  its  magnetic  properties,  that  it  giv(>s  a  crackling  tone 
both  whi'u  matle  into  an  open  tube  which  surrounds  the  coil, 
and  also  when  jilaced  alongside  of  it.  The  tone  in  this  case  is 
similar  to  that  heretofore  notieed  in  sheet  iron  when  laid  in  the 
coil,  but  it  is  much  weaker  than  that  heard  when  the  edges  of 


TONES    PKODUCED   HY  ELECTKIUITY. 


141 


the  tube  come  in  contact  In  the  latter  case  it  seems  as  though 
a  second  tone  appears  with  the  former  one. 

The  sounds  obtained  in  this  manner  from  metallic  tubes 
whose  edges  just  come  in  contact  with  each  other,  arc  evidently 
produced  l)j  the  induced  current  generated  in  the  mass  of  the 
tubes  by  tlie  action  of  the  intermittent  current  in  the  coil.  They 
must  evidently,  therefore,  become  strong(>r  or  weaker  as  the  con- 
ditions which  give  rise  to  them  render  the  induced  current 
stronger  or  weaker.  For  example,  they  are  increased  when  iron 
wires  are  placed  in  tlie  coils,  as  was  done  in  the  experiments 
made  by  the  writer.  They  are  also  increased,  but  in  a  smaller 
degree,  when  tlie  coil  is  connected  with  a  condenser,  which  was 
also  done  in  all  of  these  experiments. 

The  weakening  of  the  tones.  iio\v(>vcr,  may  be  still  more 
strikingly  shown.  For  this  pui'posc  it  is  only  necessary  to 
place  bclwccn  the  tube  producing  the  tone  and  the  induction 
coil  another  metallic  tube,  comiilctdy  closed  and  of  somewhat 
smaller  diameter.  As  somh  as  this  is  done,  the  tone  of  the 
wider  tube  ceases  inst;.  ,  ly,  and  when  the  smaller  tube  is 
withdrawn  again  the  tone  lunence-;    it  once. 

Even  two  tubes  of  dill'ercnt  diameti  •  -  capable  alone  of  g' .  mg 
out  tones  will  show  this  weakening.  Imu  if  placed  simultaneously 
one  within  the  otiicr  around  the  coil,  the\  do  not  inli  fere  with 
each  other. 

In  ])lace  of  the  smaller  closed  tube,  which,  for  example,  may 
consist  of  zinc  or  any  other  non-magnetic  metal  an  open  iron 
tube  may  bo  substituted.  In  this  case  also  the  action  depends 
u]ion  the  length  and  thickness  of  the  metal,  and  weakens  or 
destroys  the  tones  accordingly;  not,  however,  becaust'ai  uluccd 
current  is  formed  in  it  as  in  the  ca.se  of  tlu>  clo.sed  y.\v-  tube,  but 
becau.se  it  becomes  magnetized  by  the  a(!tion  of  the  I'oil,  just  a.s 
the  c(jre  does,  and  the  effects  of  the  coil  and  core  consequently 
oppose  each  other. 

The  ]n-oof  of  the  connection  of  the  tones  with  the  induced 
current,  if  additional  proof  is  nece.s,sary,  is  still  further  shown  by 
the  fact  that  they  are  quite  iadependent  of  the  diameter  of  the 


142 


THE   SPEAKING   TELEl'IIOXE. 


tubes.  The  writer  has  obtained  tones  from  tubes  of  two,  four, 
and  ei<ilit  inclics  diameter  without  noticin'r  any  diii'erenee  in  the 
stren;:rtli  of  tlie  sound,  otlier  tlian  wliat  niiglit  be  attributed  to  a 
change  of  im>])ortion  between  the  length  and  diameter  of  the 
tubes. 

With  projiortionatc  length,  a  hollow  evlimler  of  any  diauietcr 
whatever  would  obviously  be  forced  by  tia;  action  of  a  single 
cell  (if  battery  to  emit  t(mes  just  as  wi-U  as  a  tube  of  onl}-  an 
inch  in  diameter 

Now,  whil(>  it  may  be  considered  sufficiently  evident  that  the 
tones  in  question  owe  their  origin  to  the  imlueeil  currents  whicii 
are  produced  in  the  tubes  ])arallelly  with  the  convoluti(ms  of  the 
coil,  and  in  this  respect  therefore  correspond  to  the  tones  gener- 
ated in  .steel  or  iron  wires  when  an  intermittent  euiTcnt  is  passed 
directly  through  the  latter,  we  must  by  no  means  conclude  that 
they  ai-e  the  result  of  a  juolecular  action  extending  throughout 
the  entire  mass  of  the  metal,  as  is  certainly  the  ca.se  when  iron 
wires  or  open  iron  tubes  arc  n«cd.  On  the  contrary,  as  the  writer 
is  fully  convinceil,  the  development  of  tones  lirst  noticed  by 
him.  has  its  origin  at  the  points  where  the  edges  of  the  tubes 
touch  each  other,  and  that,  in  consequence  of  this,  slight  concus- 
sions occur  which  set  the  tubes  to  vibrating  and  thus  give  out 
tones. 

The  tones,  moreover,  are  only  a  secondary  phenomenon,  and 
may  entirely  fail  wlien  the  material  of  which  the  tubes  are  made 
possesses  but  little  elasticity,  as,  for  instance,  when  lead  is  u.-^ed. 
'riic  real  part  of  th(>  acoustical  ])henomenon  lies  in  the'dull  sound 
or  kind  of  ticking,  .somewhat  similar  to  that  of  a  watch,  which  is 
heard  at  the  points  where  the  edges  come  in  contact  .simultane- 
ously with  the  strokes  of  the  vibrating  hammer. 

It  is  consequently  this  ticking  alone,  and  not  the  tone  produc- 
tion, whose  investigation  properly  comes  witliin  the  province  of 
electrical  science,  an  '  which  I  eonser|uently  made  the  especial 
subject  of  .study,  but  U])  to  the  present  time  I  am  obligeil  to  sav 
I  have  not  yet  succf  ded  iu  bringing  about  a  complete  solution 
of  the  problem. 


TONES   PRODUCED   BY  KLECTRICITY. 


143 


The  tickinf^  tone  is  not  anrlihlo  in  a  tube  whose  edges  have 
been  soldered,  and  thus  prol)ab]y  made  to  resemble  more  nearly 
a  hollow  oast-ii'on  cylinder.  ICven  a  soldered  t\xl)e.  which  has 
l)een  so  nearly  cut  in  two  that  oidy  a  ])orti()n  of  metal  of  about 
a  line  in  width  remains,  is  found  to  give  no  ticking  sound  nnder 
the  conditions  I  employed. 

This  shows  that  a  certain  se]iaration  of  the  cdgc.^s  is  required 
for  the  production  of  the  sound;  it  is  furthermore  perfectly 
clear  that  the  adja(!ent  edges  of  the  tnbe  do  not  come  in  so  close 
contact  as  the  ]iaiticles  within  the  ma.ss,  and  is  also  proven  by 
phenomena  in  other  provinces  of  physical  science.  With  ap- 
parently the  very  best  contact,  also,  wc  must  admit  the  exist- 
ence of  a  thin  air  stratum  between  the  edges  of  the  tube,  the 
same  as  exists  even  in  the  dark  centre  of  Newton's  rings. 

The  influence  which  distance  between  the  edges  of  the  tubes 
has  on  the  ticking  is  shown  by  the  fact  that,  the  more  the  edges 
are  pressed  together  the  greater  is  the  decrease  in  the  sound,  and 
it  is  not  improbable  therefore  that  if  the  compression  were  in- 
creased with  force  sufficient  to  press  tlie  partii'lesof  metal  firmly 
against  each  other,  the  scmnd  could  be  eutii'clv  destroyed.  On 
the  other  hand,  again,  if  a  loud  sound  is  wanted  it  is  necessary 
to  make  the  edges  just  touch  each  other  loosely. 

It  might  be  thought  an  increase  of  ].ressui'e  would  increase 
the  number  of  contact  jioints  also,  and  in  this  manner  cuuse  the 
decrease  in  the  strength  of  the  sound.  This  coidd  only  have 
been  the  case  when  I  caused  greater  portions  of  the  edges  of  the 
tubes  that  were  not  quite  parallel  to  a])proa('h  each  other,  so  that 
in  general  such  a  conclusion  will  hardiv  be  found  to  hold  good. 
It  has  furthermore  been  found  that  when  a  short  piece  of  wire 
or  a  sewing  needle  is  placed  between  the  edges  of  the  tube,  the 
ticking  then  bccoiues  very  loud,  but  decreases  in  like  manner 
with  increased  pressure,  although  the  needle  is  never  made  to 
touf^h  at  all  points. 

Portions  of  the  tube  edges  may  also  be  in  close  metallic  con- 
tact without  tlu!  entire  disajipcarancc  of  th(>  ticking  if  ouly  other 
portions  make  but  slight  contact  with  each  other.      Hence  tubes 


144 


THE   SPEAKING  TELEPHONE. 


which  have  hoeii  partially  cut  in  two,  like  those  previously 
meutioned,  will  oonuuonce  to  give  out  sounds  if  a  needle  or 
wedge-sliape  })iece  of  luetai  is  inserted  in  the  slit.  This  exj)l;tins 
a  pheuonienou  which  is  observed  with  tin.  When  a  sheet  of  this 
metal  is  bent  around  the  induction  coil  and  its  edges  are  brought 
close  to  each  other,  they  immediately  become  fastened  together 
as  if  soldered,  and  yet  the  ticking  continues  to  be  heard  exceed- 
ingly well,  if,  however,  the  neighboring  edges  are  melted 
together  with  a  spirit  flame  or  soldering  iron,  the  soimd  ceases. 

The  principal  rpiestion  in  this  examination  is  of  course  this: 
Wiiat  causes  the  tickingsound  at  the  divided  edges?  On  lirst 
consideration  it  might  be  attributed  to  the  ]iassage  of  sparks,  but 
this  certainly  is  not  the  origin  of  the  sound.  Sparks  may  gener- 
ally be  .'Jeen  by  separating  the  edges  of  the  tubes  from  each  other 
at  the  moment  the  hammer  interrupts  the  l)attery  current.  Tliey 
are  also  noticed,  but  in  a  lesser  degree,  with  tubes  which  have  been 
partially  cut  in  two,  when  the  wedge  is  allowed  to  drop  into  the 
opening.  But  so  long  as  tlie  edges  remain  quietly  near  each 
other  no  spark  is  observed,  even  in  perfect  darknes.s  and  yet 
.the  ticking  continues  all  the  time  without  the  slightest  inter- 
Iruption.  I  further  placed  the  induction  coil  with  tiie  metallic 
'tube  under  the  exhausted  receiver  of  an  air  ])mnp,  but  even 
there  the  ticking  was  heard  without  the  least  .s])ark  being  visible 
between  the  edges  of  the  tube. 

The  sparks,  moreover,  ])ossess  an  exceedingly  low  potential, 
but  this  is  not  to  be  wondered  at  when  we  consider  tliat  they  are 
produced  in  a  metallic  conductor  of  only  a  few  inches  in  length. 

With  ca.sily  fusible  metals,  such  as  tin  for  example,  sparks  ar(> 
often  seen  to  be  projected  for  a  distance  of  several  lines,  but 
these  caimot  be  considered  as  genuin(!  electrical  sparks  ;  they  are 
cau.sed  rather  by  the  projection  of  particles  of  melted  and  glow- 
ing metal,  and  their  direction  also  is  generally  contrary  to  that 
of  the  electrical  current,  being  sometimes  towards  one  side  and 
sometimes  towards  another.  In  any  case,  however,  they  can 
never  be  real  electrical  sparks,  since  the  electrical  ])otential  of  the 
current,  as  already  stated,  is  too  low  for  their  production.     It 


TOXES    PHODL'CED   BY    ELECTRICITY. 


145 


made  no  difftM-enco  how  near  I  brought  tlic  edges  togethei-  witli- 
out  causing  alisoliite  contact,  I  could  never  preceive  the  i)as- 
sage  of  sparks  between  them.  The  sbght  space  miglit  also  be 
closed  1)}'  tiie  moistened  lingers,  or  the  tip  of  the  tongue  even 
might  he  placed  between  the  edges  of  tlie  tuljes  without  feeling 
the  sliglite--t  sensation. 

If  Sjiarks  were  the  cause  of  the  sound  one  would  naturally 
suppose  it  woidd  disappear  in  a  (luid  conductor,  but  while 
maintaining  the  tube  in  a  horizontal  position,  1  have  dipped  its 
edges  III  s])ring  v>-ater,  and  even  in  diluted  sulphuric  acid,  without 
being  able  to  perceive  any  decrease  in  the  sound.  When,  how- 
ever, a  thin  piece  of  blotting  paper,  which  has  l)een  saturated 
with  diluted  sulphuric  acid,  is  placed  hetween  the  edges,  and 
consecpicntly  the  metallic  contact  is  broken,  the  sound  disap- 
jtears.  It  also  disappears  with  zinc  tubes  when  the  edges  ai-e  so 
thorougldy  amalgamated  that  drops  of  mercury  remain  adhering 
thereto,  obviously,  however,  l)ecausc  perfect  metaUic  contact  i.s 
thus  established. 

On  the  other  hand,  again,  the  sound  did  not  cease  when  tho 
edges  wert'  highly  heated  by  the  flame  of  a  sjiirit  lamp,  but  a 
decrease  in  its  loudness  was  certainly  n<iticeabl(\ 

The  question  therefore  presents  itself  still  more  forcibly.  If 
sp;irks  do  not  produce  tlie  sound,  what  then  is  the  cause  that 
does  ? 

We  might  attribute  it  to  a  kind  of  repulsion  such  as  that 
which,  as  has  been  shown  by  Ampere,  exists  between  diil'erent 
elements  of  a  current  for  each  other.  It  is  possible  that  during 
the  time  the  mirrent  is  being  generated  this  repulsion  causes  the 
edges  of  the  tubes  to  sejKirate  a  little,  and  on  its  disappearance 
allows  them  to  approach  each  other  again.  This  alone,  however, 
is  not  sufficient;  it  seems  hardly  possible  that  these  weak  cur- 
rents could  produce  such  dispropoi-tionate  mechanical  results. 
1  have  noticed  the  sound  in  zinc  tubes  of  two  inches  diameter 
and  over  two  and  a  half  lines  thickness,  which  required  consider- 
able cilort  to  bring  the  edges  together.  Besides,  however  much 
we  may  incline  to  the  idea  that  the  sound  results  from  a  me- 


140 


THE  SPEAKING  TELEPHONE. 


chanical  knocking  of  the  cdj^cs  together,  ol)servation  so  far  has 
given  no  proof  lliat  sueh  is  tlic  case. 

To  the  unassisted  eye  the  edges  seem  to  remain  absolutely  at 
rest,  and  even  when  viewed  in  the  microscope,  magnifying  at 
least  a  hundred  times,  which  would  seem  powerful  enough  to 
show  any  sueli  motion  if  it  existed,  wo  are  unable  to  ])erceive 
any  change.  In  addition  to  this  also,  the  li([uids  in  which  the 
ticking  tubes  wen;  dijtped  .sho\ve(l  no  signs  whatever  of  the 
slightest  tremor  or  undulating  motion,  so  that  the  ticking  and 
toning  vilirations,  if  such  they  realhj  m\\  nnist  be  extremely  small. 

The  mo.st  natural  view  of  the  pheiioiuena  is,  that  notwith- 
standing tlie  ai)i)arent  metallic  contact  of  the  edges  of  the  tubes, 
no  uniform  How  of  electricity  actually  follows,  but  tluit  as  the 
current  is  interi'upted,  a  sudden  discharge  docs  take  place,  with- 
out, howcn'cr,  the  appearance  of  spark.s. 

This  assumption  may  seem  to  be  a  very  extraordinai-y  one, 
but  at  the  same  time  it  cannot  be  said  to  contradict  the  experi- 
ence heretofore  obtained :  there  seems  to  i)C  no  real  ground  for 
asserting  that  the  ])as.sage  of  electricity  througii  an  cxccedingl}' 
thin  stratum  of  air  should  necessarily  be  accompanied  by  .s2)arks, 
while,  on  the  contrary,  aigumcnts  may  be  adduceil  to  show  that 
the  appearance  of  sparks  under  similar  circumstances  is  some- 
what doubtful.  It  still  remains  an  open  (picstion  whether,  in 
the  sparks  as  they  a])pear,  we  really  see  the  strbstantial  transfer 
of  electricity;  these  .sparks  may  just  as  well  be  only  accompany- 
ing yjhcnomena  of  a  dark  invisible  di.scharge  of  electricity,  and 
their  comparatively  slow  motion  in  certain  cases  would  .seem  to 
render  this  view  not  altogether  im])robablc, 

I  do  not,  however,  purpo.sc  forming  an  hyjiothcsis  here,  and 
additional  light  on  the  phenomena  in  question  must  be  derived 
from  future  observations. 


ELECTRICAL  TRANSMISSION    OF  SPEECH.  ^ 

I  have  not  thought  it  desirable  to  give  ])roniinence  in  this 
chapter  on  the  Electric  Telegraph  to  a  fantastic  idea  of  a  cer- 

1  Expos6  dos  upplioations  do  I'electrioitiJ.   Paris,  1857,  par  LoCto.  Th.  BuMonccl. 


TKOPAGATIOX   OV  TOXES   BY   ELECTIUCITY. 


147 


tfiin  M.  Ch.  Bonrscillos,  who  liolicvos  tliat  wo  shall  ho  able  to 
transmit  spcec'li  liy  chx'tririty,  for  it  might  Ik;  ask('(l  why  I  class 
amongst  so  many  i^cmarkahK;  invontioiis  an  idea  wiiicli  is  at 
present  only  a  dream  of  its  aiilhor.  Nevertheless,  as  I  am  honnd 
to  1)0  faithful  to  the  duty  1  have  undertaken  of  mentioning  every 
electrical  aii])lieation  whieh  has  come  to  my  knowledge.  I  will 
give  you  some  details  whieh  tin;  author  has  ali'eady  j)ul)lislied 
on  this  subject  He  says:  I  ask  myself,  for  exam])l(>,  if  wonls 
themselves  cannot  he  transmitted  by  electricity ;  in  other  words, 
if  one  could  not  speak  at  Vienna  and  make  oneself  heard  in 
Paris — the  thing  is  practicable,  and  T  will  show  you  how. 

Imagine  that  you  sjteak  against  a  sensitive  plate,  so  flexible 
as  to  lose  none  of  the  vibrations  jirodueed  by  the  voice,  and  that 
this  plat(!  makes  and  breaks  successively  the  conununieation 
with  an  electric  Jiile;  you  may  have  at  any  di.stanee  another 
plate,  which  will  undergo  in  the  .<ame  time  the  same  vibration. 

It  is  obvious  that  numberless  ajiplications  of  high  importance 
Would  immediately  ari.se  out  of  the  transmi.ssicjn  of  speech  by 
electricity;  any  one  who  was  not  deaf  and  dumb  could  nuike 
use  of  this  mode  of  tran.smission,  which  would  not  reijuire  any 
kind  of  aj)paratus, — an  electric  pile,  two  vibratory  ])late.s,  and  a 
metallic  wire  are  all  that  would  bo  necessary. 

In  any  ease,  it  i.s  certain  that  in  a  future,  more  or  less  dis- 
tant, s[)eech  will  be  transmitted  to  a  distance  by  electricity.  I 
have  eonunenced  exjicrimcnts  with  this  object:  they  are  delicate 
and  require  time  and  patience  for  their  develojuuent.  but  the 
approximatious  already  obtained  give  promise  of  u  fu\orable 
result. 

PROPAGATION   OF   TONE.S  TO   ANY   DISTANCE   BY   MEANS  OF 
ELECTRICITY.  ^ 

Previous  to  1840,  the  attempts  to  transmit  signals  to  great  dis- 
tances by  means  of  electricity  were  not  very  successful.  Since 
that  time,  howevei',  great  advancement  has  been  made,  and  tele- 


Bottgur's  I'olytecluucol  Notezblatt,  1863. 


148 


TlIK   SPEAKING  TELEPHONE. 


graph  wii'os  aro  now  so  generally  erected  througliout  the  ('ountry 
tliat  it  leaves  little  to  be  desirod. 

Experiments  luivo  bei'n  iriadc  to  traii-init  tones  to  any  dcsireil 
distance  by  means  of  electricity.  'I'lie  lirst  experiment  wliieh  was 
in  ;iny  degree  successful  was  made  l)y  Philip  Heiss,  professor  in 
natural  j)hilosophy  at  Fricdrichsdorf,  near  I'Vatikfort  on  theNfain, 
anil  repeated  in  the  meeting  room  of  the  I'hysieal  Society,  in 
Frankfort,  on  the  26th  of  October,  1801,  before  a  largo  number 
of  members.  One  i)art  of  his  apjiaratus  was  set  up  in  the  Civic 
Hospital,  a  building  about  three  hundred  feet  distant  from  the 
meeting  room,  the  doors  and  windows  of  the  l)uililing  being 
closed.     Into  this  apparatus  he  caused  melodies  to  be  sung,  and 


Fiij.  G8. 

the  same  were  rendered  audible  to  the  members  in  the  meeting 
room  by  means  of  the  second  part  of  his  a})paratus,  Tlie  a])pa- 
ratus  used  to  obtain  this  wonderful  result  is  sliown  in  (ig.  08,  a 
small  light  wooden  box  in  the  form  of  a  hollow  (;ube,  having  ^ 
hirge  and  a  small  aperture  at  each  end.  Over  the  small  open- 
ing was  stretched  a  very  fmo  membrane,  5,  against  the  centre  of 
which  rested  a  small  platinum  spring  e,  which  was  fastene(l  to  the 
wood.  Another  strip  of  platinum yj  likewise  fastened  at  one  end 
to  the  wood,  had  a  line  horizontal  peg  inserted  in  the  other  end, 
which  peg  rested  on  the  platinum  spring  at  the  point  of  contact 
with  the  membrane.  As  is  well  known,  tones  are  generated  by 
the  condensation  and  rarefaction  of  the  air  taking  place  in  rapid 


Jin 

th 

an 

lio 

bu 

ru 

th: 

\va 

sec 

int 

th^ 

i]'o 


KEISS9   MUSICAL  TELEPHONE. 


149 


und 


succession.  If  these  motions  of  the  air,  called  waves,  strike  the 
thin  inenil)rane  they  cause  it  to  vihrate,  which  forces  the  phit- 
inu'.u  spring  resting  upcju  it  against  the  horizontal  peg  inserted 
in  the  second  platinum  strip,  whicli  hops  up  and  down  with  it. 
Now,  if  the  hitter  he  connected  liv  ;i  wire  with  one  of  the  poles 
of  a  galvanic  battery,  ami  the  electricity  conducted  by  a  wii'c  at- 
tached to  tlie other  pole  of  the  battery,  to  any  desired  distance, 
then  through  a  helix,  ii,  six  inches  Ion;',  formed  of  very  fine  spun 
eo])])er  wire,  and  thence  back  to  the  platinum  spring  on  the  trans- 
mitting a])paratus — then  at  cyt'vy  vibration  of  the  membrane  an 
interruption  of  the  electric  current  will  take  place.  Through 
the  opening  in  the  helix  above  described,  an  iron  bar  ten  inches 
long  is  run,  the  ends  of  which  prciject  about  two  inches  and  rest 
uj)on  two  .sticks  of  a  sounding  boai'd. 

It  is  well  known  that  when  an  electric  current  passes  through 
a  helix  enclosing  an  iron  rod  in  the  manner  described,  at  each 
interruption  of  the  current  atone,  produced  by  the  elongation  of 
the  rod,  is  audible.  When  the  interruptioris  follow  each  other 
at  a  moderate  rate,  a  tone  is  generated  (owing  to  the  change  in 
position  of  the  molecules  of  the  rod)  which  is  known  as  the 
longitudinal  tcjiie  of  the  bar,  and  which  dej)ends  upon  its  length 
and  the  strength  of  the  current.  If,  however,  the  interruptions 
of  the  electric  current  in  the  helix  take  jilace  more  rapidly  than 
the  movements  of  the  molecules  of  the  iron  bar,  which  arc 
limited  by  its  elasticity,  then  they  are  not  able  to  complete 
their  course,  and  the  movements  con.serpiently  become  smaller 
and  (piicker  in  proportion  to  the  ra})idity  of  the  interrup- 
tions. The  iron  bar  then  doci  not  emit  its  longitudinal  tone, 
but  a  tone  who.se  jntch  is  dependent  uj)on  the  nund)er  of  inter- 
ruptions of  the  em-rent  in  a  given  time.  It  is  a  well  known  fact 
that  higher  and  deeper  tones  de])cnd  upon  the  number  of  air 
waves  which  .succeed  each  other  in  a  second's  time.  We  have 
seen  heret<jfore  that  on  these  air  waves  de[)end  the  number  of 
interruptions  of  the  electric  current  of  our  apparatus,  through 
the  agency  of  the  membrane  ami  the  platinuni  strips,  and  the 
ii'on  bar  consequently  should  emit  tones  of  the  same  pitch  as 


150 


TIIK   SPEAKING   TELEI'IIONK. 


tlioao  acting  upon  the  niernbrano.  Tones  may  thus  bo  repro- 
ihu'cil,  with  a  good  apparatus,  at  almost  any  ilistance. 

It  is  evident,  tlierefore,  that  it  is  hy  llio  clectrio  impulses 
alone,  and  not  by  the  transmission  of  the  sound  waves  them- 
selves through  the  wire,  that  the  tones  become  audibc  at  the 
distant  end,  for  the  tones  are  no  longer  apparent  wlien  the  ter- 
minal wires  of  the  helices  are  joined  by  a  metallic  conductor, 
and  thus  the  instrument  shunted  out  of  circuit. 

Tlie  reproduced  tones  are  generally  somewhat  weaker  than  the 
original  ones,  but  tlie  numljcr  of  vibrations  is  always  the  same. 
Conse(|Ucntly,  while  wo  may  easily  reproduce  precisely  the  same 
pitch  of  the  tone,  it  is  dilliodt  for  the  ear  to  determine  the  dif- 
ference in  the  amplitude  of  the  vilirations,  on  account,  of  the 
gradually  decreasing  vibrations,  which  limit  even  t'/i  v'-ikcr 
tones.  The  nature  of  the  tone,  however,  de[)cnds  u[)on  the 
number  of  the  vibrations — that  is  to  say — tones  of  the  same  i)iteh 
are  ])roduced  by  the  sumo  number  of  waves  per  second — at  the 
same  time  each  wave,  as,  for  instance,  the  4th,  (jth.  etc.,  may  be 
stn^nger  than  any  succeeding  wave. 

Scientists  have  shown  that  when  an  elastic  spring  is  made  to 
vibrato  by  being  struck  by  the  teeth  of  a  cog-wheel,  the  lirst 
vibration  is  the  strongest,  and  each  succeednig  one,  less.  If, 
before  tlie  spring  stops,  it  is  again  struck,  then  the  next  vibra- 
tion becomes  equal  to  the  iirst  vibration  of  the  lirst  strok'>— 
without  the  spring,  however,  making  more  vibrations  on  that 
account. 

It  may  be  tliat  the  time  is  still  distant  when  it  will  be  ])ossible 
for  us  to  hold  a  converstition  with  a  friend  at  a  distance,  and  to 
distinguish  his  voice  as  if  he  were  in  the  same  room  with  us. 
Still  the  probability  of  success  in  this  has  become  as  great  as  it 
was  during  the  important  experiments  of  Xiepce  for  tlie  repro- 
duction of  the  natural  colors  by  photography. 


CnAPTKR  A^ 


GRAY  S  'lELKI'lIOXK!   ItKSKAUCIIES. 


*  While  engaged  in  studying  tbo  iihciiouieniuif  induced  cur- 
rents, I  had  noticed  a  sound  pnjceeding  fmiii  an  I'k'ctro-nmgnct 
connected  in  tlic  secondary  circuit  of  a  small  Klimukorfr  coil, 
wliicli  was  at  that  time  in  o|icratioii.  'i^liis,  of  course,  was  not 
new  (it  having  hccn  ol)serve(l  by  Page.  Henry  and  others  that 
tho  iMiignetization  of  iron  is  acconii»anied  with  sound),  hut  it 
helped  to  direct  my  mind  to  the  subject  of  transmitting  musical 
tones  telegra|ihieally.  Subse([uently  I  mailo  a  discovery  that 
]rd  to  a  thorough  investigation  of  tlio  subject,  and  I  have  de- 
vnted  my  whole  time  since  then  to  tho  study  which  it  suggested. 

'riu!  circumstance  was  a.s  follows:  My  nephew  was  ]ilaying 
with  a  small  incbiction  coil,  and,  as  iio  expressed  it,  was  ''taking 
shocks  "for  tho  amusement  of  the  smaller  children.  ]Ie  Jiad 
connected  one  end  of  tho  secondary  coil  to  the  zinc  bning  of  the 
batli  full,  which  was  dry  at  that  time,  nulding  tho  other  end  of 
tlio  coil  in  liis  left  hand,  ho  touched  the  lining  of  the  tub  with 
tho  right.  In  making  contact,  hi.s  hand  would  gliile  along  tlio 
side  for  a  short  distance.  At  these  times  1  noticed  a  sound  pro- 
ceeding from  under  his  hand  at  the  puint  of  contact,  which 
seemed  to  have  tiie  same  jiitch  and  quality  as  that  of  tlu;  vibrat- 
ing elcctrot(jme,  which  was  within  hearing.  I  immetbately  took 
the  elcctrodo  in  my  hand,  and,  repeating  th(^  operation,  to  my 
astonishment  fouml,  that  by  rubliing  liard  and  ra[iidly,  1  could 
make  a  much  louder  sound  than  tho  clectrotome  was  makhig. 
I  then  changed  the  pitch  <^f  the  vibration,  increasing  its  rapidity, 
and  found  that  the  ])itch  of  the  sound  under  my  hand  was  also 
changeil,  it  still  agreeing  with  that  of  the  vibration.  I  then 
moistened  mv  hand  and  continued  the  rubliing,  but  no  sound 


1  Experinit'iital  Ro.sciirelii's  by  Elislm  (Iniy.     Kcml  before  tlio  Arncrioan  f^lectri- 
(Mil  Suc'iotv,  Miircli  17,  is;,';. 


152 


TIIK   SPEAKIXa   TELEPHONE. 


was  pri)(lu('('(l  so  ]impf  as  mv  I'avid  roinaincd  wpt  :  Imt  as  soon  as 
tlic  parts  ill  coiitacl  bocaiiu'  ilrv  tlu>  soiiml  iva])pear('il. 

Tlu^  next,  sicj)  was  t<>  coiistriicl.  a  koy  lioaivl,  with  a  raiiixo  at 
first  of  one  octave,  similar  in  appearance  to  llio  cut  shown  in  lig. 
69,  Avliich  has  two  octaves. 

Each  key  lias  a  steel  reed  or  electrotnme,  tuned  to  correspond 
to  its  jiosition  ill  the  nuisieal  scale.  A  better  understanding 
of  tlie  operation  of  a  key  and  its  corresponding  clcctrotonic  may 
lu'  obtained  by  re ferrinir  to  the  detached  section  shown  in  fur.  70. 


Fig.  69. 

a  is  a  steel  reed  tuned  to  \'ibratc  at  a  deliiiite  rate,  correspond- 
ing to  its  jiosition  ill  the  scale.  One  end  is  I'igidI}' ii-\.ed  to  the 
jiost  (j.  while  the  other  ciid  is  left  free,  and  is  actuatc<l  by  a 
local  battery.  'I'he  niagin'ts  e  and  _/' arc;  arranged  in  the  same 
local  circuit,  magnet  j'  having  a.  I'csistauci'  of  about  thirty  ohms 
and  magnet  e  ahout  four  ohms.  \\  lien  tiie  i'ee(l  a  is  not  in 
vibration  tiie  point  //  is  in  electrical  comact  wi'h  it,  which  throws 
a  shunt  wii'e,  entirely  arouml  the  niagncly'.-  thus,  jiraetically,  llie 
whole  of  the  local  current  passes  through  magnet  t-  at  IIk!  instant 
of  closing  tht^  ke\- '•.  Jt,  is  well  known  that  wlicn  twoelecti'o- 
juaguets  are  jiiaccd    in    the  .-aiae  circuit,  the  one  which  has  the 


gray's  telephonic  keseakches. 


158 


liitrhcr  rosistancc  (other  tilings  ])oing  oqnal)  will  dovclnp  the 
stronger  magnetism,  ;mil  that  if  tiic  magnet  of  higher  resistance 
be  taken  ont  of  the  circuit  the  force  of  the  other  will  be  increased. 
When  the  key  c,  being  depressed,  closes  the  local  circuit  at  d, 
the  operation  of  the  rcc(l  is  as  follows:  'riiewholc!  of  tlie  (•urrent 
from  battery  l  'a  passes  through  the  ningnet  -",  uliich  attracts  the 
reed,  say  with  a  ])ower  of  four.  When  the  reed  has  moved 
towards  i  far  enough  to  leave  the  Jioint  rj.  the  shunt  circuit  is 
lu-okeii  and  the  current  flows  through  lioth  the  magnets.  Ln- 
mediutely  the  power  in  /  rises  from  zei'o  t<j  live,  and  that  of  e 


-  7JI.  5. 


,  Unrlh 


Fi'J.  TO. 

drops  from  four  1o  oni\  and  the  i-eed  is  attracted  towards/  with 
an  ellecti'i!  foivc  of  four,  until  contact  is  again  established  with 
the  ]ioint,7.  ''"'"'  opei'ation  is  ivitcateil  iit  a  rate  determined  l)y 
the  si/.e  and  IfUii.h  of  the  reed,  and  wliifli  ci  I'lvsponds  with  tlie 
liiud.'imcntal  oi  the  note  it  represents.  The  ligmvs  given  above 
onlv  apiiro.ximate  t'^e  facts.  'J'lic  relation  of  the  magnets  as  to 
si/e  and  resistance,  .so  as  to  liive  an  eipial  impulse  to  the  reed  in 
both  direelions,  was  di'termiued  by  actual  experiment  with  a 
batterv  of  a  gi\cn  size. 

It  will   be  observed   that   bv  ihis  .Mrrangenu'ut  the  centre  of 
vibration  coincides  with  the  (■eutrc  vi  the  iced  when  at  rest,  so 


154 


THE    SPEAKING    TELEPHONE. 


that  tho  pitch  of  the  tone  is  not  disturbed  1)y  any  ordinary  change 
of  l)atter3%  as  is  liable  to  l>e  tiie  case  when  <jiily  one  magnet  is 
used  or  when  the  impulse  is  not  equal  in  both  directions. 

\  second  battciy,  which  we  will  call  the  main  battery,  is  con- 
nected as  follows:  One  pole  is  connected  to  the  ground,  '^l^hc 
other  runs  to  the  instrument,  and,  entering  at  binding  screw  -i 
(fig.  70),  runs  to  point  ft  of  key  c ;  from  key  c  to  point  t. 
which  makes  contact  with  the  reed  a;  from  reed  «  to  binding 
S(-re\v  1,  and  thcnt'C  to  line.  It  will  be  seen  that  when  the  key 
is  at  rest  the  batteries  are  open  at  the  ]ioints  d  and  h. 

All  the  keys  in  the  instrument,  whether  one  oi-  more  octaves, 
have  corrcsi)onding  reeds  and  actiuiting  magnets,  the  only  dilTer- 
ence  being  in  the  tuning  of  the  reeds.  There  is  but  one  main 
and  one  local  battery  used,  and  the  connections  to  each  key  are 
run  in  l)ranch  circuits  from  the  l)inding  screws,  as  shown  in  iig. 
69.  But,  since  all  th(>s(3  branclu>s  are  open  at  the  key  jjoints, 
neither  of  the  batteries  is  closed  unless  u,  key  is  tlcprcssed. 

If  now  the  keys  are  manipulated,  a  tune  maybe  ])laycil  which 
is  audible  to  the  jtlayer.  When  any  key  is  depresse(|,  the  local 
battery  sets  in  vibration  its  corresponding  reed,  which  sounils  its 
own  fundamental  note  according  to  the  law  of  acoustics.  So  far 
the  instrunu'nt  is  an  electrical  oi-gan,  the  motive  ]iower  being 
electricity  instead  of  ;iii-.  The  main  battery  has  had  no  j'art 
whatcN'cr  iti  its  operation. 

]f,  however,  the  mniii  circuit  is  closed  by  connecting  the  (lis- 
taiit  end  to  ground,  au<l  the  ]Miint  i  is  properly  adjusted,  so  that 
it  mak'es  mid  breaks  contact  ^vitll  the  reed  iit  each  viliration,  a 
series  of  e!cctri<^  imjiulses,  or  waves,  will  \h'  sent  tiiroiigh  the 
line,  corresponding  in  numlier  per  second  to  the  fundamental  of 
the  rceil. 

Now,  as  the  jiitcli  of  aii\' musical  tone  is  ilelerminei]  bv  the 
number  of  \iiirations  per  second  made  li\'  the  sulistaiicc  from 
which  the  ^ound  proceeds,  it  is  clear  that  if  these  <'lectrieal  waves 
can  be  eonsi'i'tcil  into  audibli  vibrations  at  tin'  distant  end  of 
the  line,  wln'tlii'r  it  be  one  mile  or  lisc  liundreil  miles  from  the 
player,  the  note  produced  will  be  of  the 
sending  reed. 


same  pitch  a,;  that  of  tlus 


GRAYS  TELEPHONIC   KESEAKCHES. 


166 


Thpi'o  arc  vai-ious  ways  hy  ^vhic]^  these  electrical  ■waves  may 
l.e  converted  into  audible  material  vibrations.  One  of  tlie  nK)st 
curious  and  novel  is  the  one  in  whicli  animal  tissue  })lays  a 
[ironiincnt  i)art.  Following  out  the  idea  suggested  by  the  l)ath- 
tub  <  .\-])eriraeiit,  I  constructed  various  devices  with  metallic 
plates  for  receiving  the  tune  liy  rubbing  with  the  hand.  A  very 
convenient  methoil  for  doing  tliis  is  sliown  in  lig.  71. 

This  instrument  has  a  metal  stand  of  sullicicnt  weight  to  keej) 
it  in  position  while  being  manipulated.  L'[ion  the  stand  a  hori- 
zontal shaft  is  mounted  in  bearings,  upon  one  end  of  which  is 
a  crank,  with  a  handle  made  of  some  insulating  substance. 
Upon  the  other  end  is  centred  a  thin  cylindrical  sounding  box, 


Fi'j.  71. 

ina(h^  of  -wood,  ilic  l';ice  ci'  wliicli  is  coveretl  witli  a  cap  made  of 
tliin  metal,  spun  into  a,  convex  form  to  give  it  lirmness.  'i'his 
lio.x  has  an  opening  in  the  centre  to  juci'intse  its  sonorous  quali- 
ties. 'I'lie  metiil  cap  is  electrically  connected  to  the  metal  stand 
by  means  of  a  wire. 

If  the  opei'utor  connects  the  c;!]!.  through  the  stand,  to  the 
:;rounil.  and  taking  hoM  of  the  end  of  the  line  with  one  hand, 
pi'essestlie  lingers  against  the  cap,  wliicii  lie  revolves  by  means 
of  the  crank  with  llie  oth-T  hnml,  tlic  tunc  that  is  being  i)layed 
at  the  othei-  end  of  the  line  liccomes  distinctly  audible,  and  may 
Ije  heard  througiiout  -a  large  audience  room.     If  tlie  conditions 


166 


THE  SPEAKING  TELEPHONE. 


are  all  perfect,  the  faster  the  plate  is  revolved  the  louder  ■will  lie 
the  music,  and  the  slower  the  motion  the  softer  will  it  become. 
When  the  motion  stops  the  sound  entirely  ceases. 

I  have  found  that  electricity  of  considerable  tension  is  needed 
to  jiroduce  satisfactory  results,  at  least  that  of  lifty  cells  of  bat- 
tery. The  necessary  degree  of  tension  is  most  convenicMitly 
obtixined  by  passing  the  line  current  through  the  primary  circuit 
(ada])ted  to  tlie  circuit  wherein  it  is  used)  of  an  induction  coil, 
and  connecting  the  receiver  in  the  secondary  circuit. 

Tlie  cause  of  this  phenomena  has  been  the  source  of  much 
speculation  and  expei'iment.  At  first,  I  supposed  it  to  be  the 
quivering  of  the  muscles  of  the  hand,  produced  by  the  electric 
im])ulses  and  connnunicated  to  the  plate  and  box,  making  an 
audible  sound,  and  that  tlie  motion  was  pro(hieed  thi-oiigh  the 
medium  of  the  nerves.  Tiiis  idea,  however,  had  to  be  aban- 
doned. While  visiting  Knghind,  in  1874.  I  called  on  Professor 
Tyndall  at  the  Koyal  Institution,  an<l  exhibited  to  him  a  portion 
of  my  apparatus.  lie  experimented  with  various  substances, 
and  found  that  the  same  result,  in  kind  if  not  in  degree,  could 
be  produced  witii  dead  animal  tissue.  For  instance,  a  l)ac<m 
rind  that  had  been  pickled  and  smoked  until  there  could  be  no 
suspicion  of  a  nervous  iniluence  left,  would,  when  sullieiently 
pliable,  ])roduce  tlie  soiind.  the  cuticle  being  used  next  tlie  plate. 

While  Professor  'IVndairs  ex|ieriinents  did  not  exj)lain  what 
the  cause  of  the  jihenomenon  really  was,  they  determineil  most 
conclusively  that  it  was  not  due  to  nervous  influence  upon  the 
tissues,  acting  in  sympatiiy  with  electrical  imjiulscs.  It  was 
suggested  by  soiiu;  that  it  might  be  caused  by  electrical  dis- 
charges, in  the  form  of  a  -^park,  from  the  hand  to  the  jilate; 
but  if  this  is  true,  why  should  uKJtiou,  as  a  gliding  of  the  hand 
over  the  surface  of  the  T'late,  be  necessa 


ry  to  ]) 


Others  have  suggested  that  the  molecules  of  the  substance  in 
contact  were  ilisturbed  ujion  the  ])assage  of  each  electrical  im- 
pulse, roughening  the  surface,  and  for  the  instant  producing  a 
sadden  increase  of  friction.  If  this  is  true,  why  should  wetting 
the  parts  in  contact  destroy  llie  effect'/ 


GRAYS  TELEPnONIC  RESEARCHES. 


157 


But  to  fontinno  my  pxporinionts:  I  noticed  that  when  rovoh-- 
iiig  the  plate  with  my  liiiiicr  in  contact,  the  friction  was  greater 
when  a  note  was  soiUKhni;-.  I  then  connected  a  small  liuhiu- 
korfl'  coil  to  a  hattery.  iiiscrtiiij^'  a  common  telegrapliic  key  in  tlie 
primary  cn-cuit.  instead  of  tlu;  self-acting  circuit  breaker.  leon- 
nceted  one  end  of  the  secondaiy  coil  to  the  metal  (ilate.  and 
lidding  the  other  end  in  my  IuukI,  I  ruhl)ed  the  plate  hriskdy. 
and  had  luy  assistant  slowly  make  dots  with  the  key.  I  noticed 
at  cacli  make  of  the  circuit  a  slight. souml,  and  at  each  hreaka  very 
innch  loud(>r  one,  owing  to  tlu;  fact  that  the  terminal  secondaiy 
M'av('  is  much  more  inten.^e  than  tlu;  initial.  J  now  held  my 
hand  still,  and,  while  T  could  feel  the  shock  just  as  distinctly  as 
hefon',  theri^  was  no  audible  soiind,  proving  that  the  motion  was 
a  ncce.ssary  condition  in  its  prodnctidii.  The  seiisatinn  when  the 
.sotmd  was  proiluecil  was  as  though  my  linger  hail  sndd(>nly  ad- 
hered to  the  plate,  and  then  as  suddenly  let  go,  producing  a 
sound. 

The  next  experiment  was  with  one  hundred  cells  of  gravity 
liattery.  I  connected  one  pole  to  the  ])late  and  held  the  othei" 
in  my  hand,  pressing  my  lingi-r  against  the  jilate  and  revolving 
it  as  before.  I  inserted  a  thin  [liecc  of  paper  between  my  lingers 
and  the  plate  to  prevent  jiaiid'ul  eifects  from  the  current,  and  my 
assistant  made  da.shes  with  a  key  in  the  circuit.  T  was  thus  able 
to  notice  the  eifect  of  an  imjml.-^e  of  longer  duration.  When  the 
key  closed  there  was  a  pen  e])tible  increase  of  the  friction,  so 
that  my  finger  took  a  position  farther  forward  on  the  plate,  where 
it  would  remain  as  long  as  thi^  circiut  remained  closed.  As  s(xin 
as  the  key  was  op<'neil  my  linger  suddenly  dropped  back  on  the 
plate,  making  the  same  noise  I  had  before  heard.  This  operation 
was  repeated  .«o  often  that  there  could  be  no  question  as  to  the 
eff(>ct  it  produced. 

From  the  foregoing  experiments,  I  hnd  that  the  following  con- 


ditions are  iieee.<sary  to  rcjiroduce   musical    tones  through 


th 


tl 


medium  of  animal  tissue,  by  means  of  electric  waves  transmitte 
gh  a  telegrai)h  wire. 
1st,  The  electrical  im]iulses  must  have  cgnsidcrublo 
in  order  to  make  the  cllect  audible. 


ML 


lion 


158 


TUE   Sl'HAKI.VG   TELKI'liUNE. 


2<1.  Tlio  siihstanco  n<c(]  for  ruhbinp;  thv>  roccivina;  plato  must 
})(•  soft  and  ]>lial)k',  uiul  iimst  lie  a  ('(inductor  of  t'lcctncity  up  to 
the  ])oint  of  contact,  and  there  <i  resistance  must  be  uiterposed, 
vci'v  thin,  ncithci'  too  ,u'rcat  nor  too  little. 

od.  The  ]ilate  anil  the  haml.  oi' other  tissues,  must  not  only  be 
in  contact,  imt  it  must  l>c  a  I'ubbini!'  or  jiiidinu'  cuntact. 

•ith.  The  paiMs  in  c<imact  must  be  dry,  in  order  U>  preserve 
tlic  nccfssai'v  dcuTce  of  I'csistance. 

It  will  he  seen  that  we  luivo  hoi'O  the  conditions  of  a  static 
charLa',  the  jilate  receiving  one  polarity  from  the  battery,  and  the 
hand  tlie  other  jiolaritv  :  the  interjiosed  resistance  ]ireveritiiig  in 
u  u'reut  deurec  the  dvnaniic  eircct.     Jt  is  a  well  known  I'uct.  that 


Jug.  VI. 

two  bodies  statically  charged  with  opposite  clcctricitios.  attract 
each  other.  May  not  this  be  the  vfhole  solution  of  the  ]ihcno- 
menon,  that  each  wave  as  it  arrives  at  the  receiving  end  becomes 
'for  a  moment  static,  which  results  in  a  momentary  attraction  be- 
tween the  ])late  and  the  ilnger,  and  this  inunediately  ceasing 
when  the  wave  is  gone,  releases  the  finger  with  a  noise  or 
sound  ?  If,  then,  sounds  are  repeated  asfa.st  as  the  .sending  i-ecd. 
vibrates,  tlic  production  of  a  musical  tone  must  follow,  accord- 
ing to  well  known  laws  of  acoustics,  providing  the  waves  are 
sent  to  line  in  musical  order. 

In  the  winter  of  1873-4,  I  experimented  very  elaborately, 
and  worked  out  many  new  .applications  of  thejn'incijtle,  not  only 
to  the  transmissiou  of  muaic,  but  to  the  transmission  of  telegraphic 


GKAYrt  TELEPHONIC   RESEARCHES. 


159 


If,  iustead  of  ilm  revolviiifi:  plato  nnd  llio  animal  tissno,  wc 
place  in  tb(^  cii'cuit  an  eloctr()-iiKi<^iH't.  or  a  mimlu'i'  of  thorn,  and 
liavc  a  lunc  playcil  at  the  traiisuiittiiiti;  end,  tlio  tunc  will  bo 
lioard  from  all  these  oloctro-iiiai^iiots.  Tlio  iimsic  jiroduood  will 
1)0  ioiid  or  low;  1st,  as  the  buttorv  used  is  strong  or  weak:  2  I, 
as  the  lino  oilers  more  or  less  resistance  ;  and  8d.  as  the  magnets 
are  mounted  moi'c!  or  less  fa\oi'alily  for  acoustic  od'eots. 

In  this  ease,  as  in  that  of  the  animal  tissue,  each  imiiulsc  pro- 
duetts  a  sound;  but  it  is  jn'oduced  diU'ereiitly  in  the  two.  It  i.s 
u  well  known  fact  that  an  ii'on  rod  elongates  wIuml  magnetized, 
and  eonti'acts  a^iain  when  dcma'/ni'ti/od.  TIk;  elongation  and 
contraction  are  so  sudilon,  that  an  audible  sound  is  ])roduced  at 
each  change.    In  order  to  convert  this  sound  into  a  musical  tone, 


o  is  only  neeessary  to  repeat  it  uniformly  and  at  a  definite  rate 
of  speed,  which  shall  not  be  less  than  sixteen  nor  mor(>  than  four 
thousand  per  second. 

When  the  electro-magnet  is  properly  mount(>d  the  tone  may 
bo  ma<le  very  loud.  Fig.  72  shows  a  very  good  form  for 
mounting  a  magnet  for  receiving  music.  It  is  a  common  electro- 
magnet having  a  bar  of  iron  rigidly  tlxe(l  at  one  pole,  which  ex- 
t(Mids  across  the  other  ])ol(\  but  does  not  touch  it  In' about  one 
KixtydVmrth  of  an  inch,  hi  the  middle  of  this  armature  a  short 
post  is  fastened,  and  the  whole  mounted  on  u  box  made  of  thin 
pine,  with  o))enings  for  acoustic  effects. 

One  of  the  earliest  discoveries  in  connection  with  those  oxp(>ri- 
mouts  was  the  fact  that  not  only  simple,  but  composite  toucs 


160 


TIIK   .SI'K.VKI.VO   TKLEPHONE. 


could  be  sont  tlinmpli  iho  wire  and  received,  either  on  tlie  metnl 
plate  or  on  tlic  uia.u'nct.  Sot  only  I'ould  a  simple  melody  be 
transmitted,  Imt  a  harmony  i>v  (hscord  could  lie  ennally  well. 
From  that  time  1  have  workccl  assiduously  with  the  view  of 
makinLT  a  ra[Hd  t('l(',L;'ra|ihic  system  cmliodyin.L^'  this  discoviay. 
The  lii'st  step  was  to  iiiialyzc  tlu'  tones  at  the  ri'ceiving  end, 
wliieh,  if  suceessfully  aeeomplished,  would  open  the  way  to  a 
multiple  Morse,  u  last  printing,  an  iiutographie  and  other  sys- 
tems. 

It  woidd  bo  impossible  to  give  in  this  paper  all  the  experi- 
ments tried,  for  they  were  very  many  indeed.  1  accomplished 
the  analysis  in  a  number  of  way.^.  The  method  which  seemed 
in  all  respects  to  give  the  be.st  satisfaction  is  as  follows: 

Fig.   73  is  a  [lerspective  of  one  form  of  a  receiving   instrii- 


I 


Fig.  74. 

inent  called  an  analyzer.  The  construction  of  the  instrument  is 
very  simple.  It  consi.sts  of  an  electro-magnet  atlapted  to  the 
resistance  of  the  circuit  where  it  is  int(>nded  to  be  used,  and  of  a 
steel  rihbou  .strung  in  front  of  this  magnet  in  a  solid  metal  frame, 
and  jirovided  with  a  tuning  .sci'cw  at  one  end,  so  aa  to  readily 
give  it  the  proper  tension.  The  length  and  .size  of  tlii'  rihhon 
depends  upon  the  note  we  wi.sh  to  receive  upon  it.  If  it  is  a 
high  note  we  make  it  thinner  and  shorter ;  if  a  low  note  we  make 
it  thicker  and  longer.  If  this  ribbon  is  tuned  so  tliat  it  will  give 
a  certain  note  when  made  to  vibrate  nu'chanically,  and  the  note 
which  corresponds  to  its  fundamental  is  then  transmitted  through 
its  magnet,  it  will  respond  and  vibrate  in  unison  witli  its  ti'ans- 
mitted  Xiotc  ;  but  if  another  note  be  scut  wliieh  varies  at  all  Ii'om 


GRAYS  TELKI'ilOXIC    KESKAKCllES. 


161 


its  fiinflamonttal.  it  will  not  rospond.  U  a  oompositc  tone  is  sent, 
the  ril)b()ii  will  rpspond  when  its  own  note  is  Ih'iul^  scut  as  a 
part  of  the  composite  tone,  Imt  as  soon  as  its  own  tf^ne  is  left 
out  it  will  immediately  stop.  Tims  I  am  al)le  to  select  out  and 
indicate  when  any  note  is  bcinu-  sent,  in  lad,  to  analyse  the  tones 
which  are  j)assin,L(  over  the  line. 

This  method  of  analyzin,u'  tones  transmitted  throuLdi  a  wire 
electrically  is  analugous  to  ili'lmlioltz's  method  of  .•^(>)>arating 
tones  transmitted  through  the  air. 

The  transmitting  instruments  n.scd  in  sending  composites  tones, 
are  made  similar  in  e\cry  rcs})ect  to  the  one  slunvn  in  lig.  70, 


A' 


-1    t- 


LINE 


CARTf-l 


except  that  each  reed  is  separately  mounted.  A  cut  of  one  of 
these  transmitters,  used  in  tclcgi'aph  work,  is  shown  in  fig.  74. 

P'ig.  75  shows  a  diagram  view  of  two  transmitters  and  two 
receivers,  with  their  connections.  T^he  local  circuits,  with  their 
magnets,  are  left  olT  to  avoid  confusion. 

A  and  ]3  rei)rcsent  two  transmitters,  placed  at  one  end  of  a 
line.  A'  and  IV,  two  receivers  at  the  other  cml.  One  end  of  the 
main  battery  is  connectcil  to  line,  and  the  other  end  to  ground. 
Each  transmitter  is  placed  in  a  slnint  wire,  running  from  its 
main  battery  cunnectiuus  around  ouc  half  of  the  battcrv,     A 


162 


TIIK    SrKAKINi;    TKLKI'lIONK. 


t'tiiiunon  open  circnit  koy  is  ])1;u;l'(1  in  cacli  of  those;  slnnit  wires. 
>5U[i|)<iso  How   the   two  reeds  ol:  A  ami   U  to  1)o  soiuidiii;.'',  A 

making  2()4:  vil)rations  per  s md,  and  W  320,  just  two  ton  's  or 

a  rnajoi-  third  aliove  A.  So  long  as  the  ke\s  remain  open,  all  the 
Lattery  is  eoii>t;n:ilv  on  the  line.  If  the  key  of  transniitver  A  is 
closeil,  lialf  of  till!  iiatteiy  is  being  thi'own  on  and  o(T  ihe  line,  at 
the  rate  of  26-1- times  ])er  second,  'i'liis  causes  a  succession  of 
electrical  wave-  to  How  tlirongh  the  line  at  tlie  same  rate.  If 
now  the  steel  i  iiou  of  the  analy/er  .V  has  lieen  tuned  in  unison 
with  these  electrical  waves,  it  will  respond  and  hum  the  same 
note  as  the  transmitter;  but,  if  it  is  not  in  unison,  it  will  remain 
practically  quiescent,  so  that  the  n(;te  can  only  be  heard  \>y  sub- 
mittinL''  it  to  the  most  delicate  test.     To  bring  it  in  unison  it  is 


Fij.  76. 

only  necessary  to  turn  the  tuning  screw  np  or  down,  as  the  case 
may  be.  When  the  fuuduracntal  of  the  ribhon  corresponds  with 
that  of  the  sending  reed,  it  .innoun(n>s  the  fact  by  sounding  out 
loud  and  full.  If  (having  the  l<(y  of  transmitter  A  still  closed, 
and  consec[uently  its  corresponding  analyzer  still  sounding)  we 
clo.sc  the  key  belonging  to  transmitter  B,  the  other  half  of  the 
battery  will  be  thrown  on  and  olT  the  line,  at  the  rate  of  320 
times  per  second,  and.  another  succession  of  electrical  waves  will 
How  through  the  line,  this  one  l)eingat  the  rate  of  320  times  per 
second.  If  the  analyzer  B'  i.s  in  projter  tune,  so  that  its  fun- 
damental is  the  same  as  that  of  its  corresponding  transmitter  B, 
it  will  hum  its  note  as  long  as  the  kev  is  closed,  making  a  chord 


GUAYS  TKI.KPllDMC   KKSEAUCUKS. 


163 


witli  A'.  Ill  tho  sivmc  way.  a  j/rriit  iiumlM'r  cif  (lilTcrcnt  )K>t03 
may  be  somidiiiL''  at  tlii;  same  tiiiif.  at  oinj  t'lul  nf  ;i  t('legra[ilii<; 
liiii',  ami  Ix;  licai'il  siiimltaru'Diisly  at  tlu^  otlicf  rml.  each  uuto 
WDimdiii^'  upon  ;i  iliHercnt  rccciviim'  iiistr-uuiciit. 

Tliu  maniHT  of  makiiiL''  tli'-si'  vil>rati()iis  of  lln-  analyzer 
operate  a  suiuuler,  a  register,  or  other  reoonliiig  iiistruiueut,  is 
shown  ill  fii'  76. 

'I'he  light  eoiitaet  lever  <•  is  ami'  1  with  a  contact  point  at  its 
free  end,  resting  merely  by  the  weigiit  of  tho  lever  itself  in  tho 
coneuve  eiip  (/,  upon  the,  extremity  of  tlie  armature  a.  When 
the  armature  is  ihi'owii  inio  \  ihratioii  tho  contact  le\'er  ho[is 
ii[)  and  down,  and  docs  not  close  tho  local  circuit  (whicli  is 
connected  to  /  and  Zj)  witii  siiliicii  i.'  linniiess  to  actuato  the 
sounder,  but  when  tho  vibration  stops  tiio  local  circuit  is  closed. 
This  I'overscs  llic  writing  upon  the  si lundii',  but  it  may  bo  op(>r- 
ateil  by  means  of  a  local  relay,  or  arrangcil  in  \;irious  other  ways 
which  readily  suggest  themselves.  'I'Im'  cmiplcto  o[ieration  is  as 
follows:  WIkmi  tli(!  o[)erat()r,  at  tlie  sending  statii^ii,  closes  liis 
key,  l]i(i  armature  n,  !>  d  is  thrown  into  vibi'aihui,  and  remains  so 
a.s  long  as  the  key  eontinucs  closed,  but  comes  to  rest  imme- 
diately when  the  k(>y  is  opeiietl.  I'Ik;  lever  c,  not  being  able  to 
follow  the  armature,  rattles  against  it  with  a  buzzing  sound,  dis- 
turbing the  continuity  of  the,  local  circuit  by  throwing  in  a 
great  resistance  at  the  point  (/.  'I'his  resistance  is  sullicient  to 
act  upon  tho  sounder  the  same,  jiractically,  as  a  dead  bi-eak.  By 
tins  means  the  sound  r  is  made  to  follow  tlio  key  of  the;  operator 
who  is  sending  the  propei-  iiDte.  In  llie  same  manner  ail  the 
other  tones  may  lie  brought  into  service,  each  igiujring  the  other, 
and  each  seeking  its  own  at  the  receiving  end. 

A  simpler  eonstruetion  i>f  tho  analyzer,  and  tMio  which  r(>n- 
ders  the  .sounder  unneees.siry,  is  shown  in  lig.  77.  The  elee- 
tro-magnet  M  M,  whicli  has  very  short  cores,  is  ]iroviiled  with 
an  arinaturo  a,  rigidly  attached  to  the  lower  core,  but  scjiaratcd 
from  the  upper  one  l)j  a  space  of  ^'^  of  an  inch.  M'his  maybe 
increased  or  diminished  hy'moviug  the  upper  core  in  or  out,  by 
means  of  the  screw  8.     Tho  armature  is  made  thinner  at  the 


164 


TIIK    SI'KAKIMI     IKI.KrilONl 


]K)int  7>,  l)cing  filnl  ilowii  until  it;  vibnitts  to  !i  cortain  nolo,  llic 
riicci-  iidjustinciit;  licing  ud'omplishcfl  l)y  adjusting  the  inov;il)k' 
weiglit  W.  'I'lic  wliolu  is  mounted  upon  ii  sounding  l)o.\  B,  open 
nt  one  nid.  wliicli  is  termed  ;i  resonator.  'I'lic  prineij  lis  involved 
in  tlio  action  oftlie  resonator  is  this  :  A  volume  of  air  eontained 
in  auopeu  vessel,  when  thrown  into  vibrations,  tends  to  yield  a 
certain  note,  and  eonseipiently  strei.gLliO'.s  lliat  note,  when  the 
latter  is  sonnded  in  its  neigliborhood.  By  placing  the  instru- 
ments upon  eorn'sjiondiiig  rcsonator.s.  the  sound  is  greatly 
strengthened,  so  that  an   operator  may  readily  read   iiy  sound 


Fig.  77. 

the  tele,gTaplii(^  charaetcns  into  which  the  continuous  tone  is 
broken  hy  the  transmitting  hey. 

Bv  tiiis  method  not  onlv  mav  diJTeront.me.ssages  Im  scntsimul- 
taneously,  hut  a  tune  with  all  its  parts  may  be  .sent  through 
hundreds  of  miles  of  wire,  and  be  ilistinetly  audible  at  the 
receiving  end. 

1  Gray's  electro-harmonic  telegraph  is  founded  upon  the  prin- 
ciple that  an  electro-magn(^t  elongates  under  the  action  of  tlie 
cleeti'ie  current,  and  contracts  agaiiL  when  the  eui'rcnt  ceases. 


* Ainor'u'aii  Mocliiinical  D'n'tinnarv.     Vol.  iii.     (Tlio  iiivciiliDii  licru  closurilnil  is  tt 
•iiodificatii)ii  ot  tUiit  slinwii  uii  liarjcs  l.j'.i  ami  \i\').) 


OKAYS   EliECTKn-IIAHMONIC   TELKl'HONK. 


165 


(-.'oiisequcntly,  u  succossion  of  impnlsos  or  iiitcrrupliouH  will 
caiisii  tlio  iiiiigiict  to  vil)ruto,  iiiul  if  tlicso  vil)i-iitioiis  ho  of  .siifR- 
ciciit  frequency,  a  musical  tone  will  \k'  pi'iMlurcd,  tln^  [litcli  of 
which  will  depend  upon  the  rapidity  of  the  vii)rations. 

By  interrupting  an  electric  current  at  the  transmitting  end  of 
a  line,  with  suflicicnt  freipicncy  to  produce  a  musical  tone  by  .ui 
instrument  vibrated  by  said  interruptions,  and  transmitting  the 
impulses  thus  induced  to  an  elcctro-mnguct,  at  the  receiving  end 
of  the  line,  tlie  latter  will  vibrate  synchronously  with  the  trans- 
mitting instrument,  and  thus  pnxUiee  a  musical  tone  or  note  of 
a  corresponding  pitch. 


Fi'j.  78. 

The  instrument  shown  in  tig.  78  consists  of  tlie  transmitting 
a])])aratus,  mounted  on  a  base  b(i:ii'd,  and  a  receiving  apparatus, 
shown  in  a  position  l)cncath  the  former.  The  induction  cuil  i' 
has  the  usual  ]>rimarv  and  .secondary  circuits.  An  onlinary 
automatic  clccti'otomc  c  has  a  circuit-clcising  S[)ring  c'l,  so 
adjusted  as,  when  in  action,  to  produce  a  given  musical  tone. 
A  connnon  telegra[ih  key  d  is  ]>Iaccd  in  the  primary  circuit  a  a, 
to  nudcc  or  break  the  l)attcry  connection.  The  key  l)eing 
depressed,  and  the  clectrotomc  C()iisc(picntlv  vibrated,  the  inter- 
ruptions of  the  current  will  simultaneously  produce  in  the  .sec- 


166 


THE   SPEAKING  TELEPHONE. 


ondarv  circuit  h  b,  of  the  i  'duction-coil,  u  scries  of  iridnccd 
curi'ents  or  iin])ulsc.s  corresponding  in  nunil)cr  with  th(3  vibra- 
tioiKs  oC  tlic  clccti'otonie,  and  as  tlic  receiving  electro-magnet  e  is 
connected  with  tliis  circuit,  it  will  "he  caused  to  vibrate  by  suc- 
cessive elongations  and  ''ontractions,  thus  ])roduciug  a  lone  of 
corresjjouding  ])itcli.  the  sound  of  which  niav  be  intensihed  l)y 
the  tise  of  a  hollow  cylinder  s,  of  metal,  placed  on  the  jiolcs  of 
the  magnet 

Wlien  a  single  electrotomc  c  is  thrown  into  action,  its  corre- 
sponding tone  will  be  repi'oduc'ed  on  the  sounder  by  the  magnet. 
When  ekrtrotomes  c  <-i,  of  dilfenMit  pitch,  arc  succ  'ssivcly  ope- 
rated by  their  respective  keys  dd^,  their  tones  will  V)e  corre- 
spondingly re])roduced  by  the  receiver ;  and  when  two  or  more 
electrotom(>s  an;  simultaneously  .sounded,  tlic  tone  of  etich  will 
still  be  reproduced  without  confusion  on  the  sounder,  so  that, 
by  these  means,  mclodi(\s  or  tunes  may  be  transmitted.  Anotlier 
system  is  founded  upon  th(>.  alternate  making  and  breaking  of  a 
telegraphic  circuit  by  means  of  the  vibration  of  tuning  forks,  or 
musical  reeds,  as  in  llelmholt/.'s  apparatus  for  the  production 
and  transmi.ssion  of  vocal  sounds.  If  a  given  fork  ])C  nutde  to 
interrupt  an  electric  circuit  by  its  vibrations,  ami  the  intermit- 
tent current  thus  procbu'cd  be  yiassed  through  a  scries  of  electro- 
magnets, each  in  coimection  with  a  fork  of  dill'erent  pitcii,  and 
consequently  dilferent  rate  of  vibration,  only  that  fork  will  be 
thrown  into  vibration  which  is  in  unison  with  the  first  one. 
Practically,  the  time  required  to  do  this  is  a  small  fraction  of  a 
second.  The  advantages  of  this  method  are  mnnerous.  Xot 
only  may  many  receiving  instnuncnts  at  one  station  be  operated, 
each  l)y  its  own  key,  through  a  single  win^  but  many  dilferent 
stations  in  the  same  circuit  may  be  o[)crate(l,  that  one  alone 
receiving  the  mes.sage  which  has  an  instrument  with  the  requisite 
pitch,  so  as  to  vilirate  in  syiK^hi'onism.  .Many  signals  nia\',  in 
this  way,  be  transmitted  over  the  .same  wire  at  the  .same  time, 
and  many  dispatches  .sent  simultaneously  to  as  many  .stations. 
^Ml  this  may  be  done,  too,  without  affecting  the  line  for  its 
ordinarv  use. 


GUAVS   ELECTRO-HARMONIC   TELEPHONE. 


167 


COMLINATIOX   OF  'I'llK   TELEPHONE  AND    MOUSE   APPARATUS.' 

The  metli(j(l  of  (■.•'iibiuiug  the  telephonic,  or  eU^ctro-liannoiiie, 
with  the  ordiiiiirv  Morse  pvstem  of  telegraphy,  invented  by  Mr. 
Eli.sha  Gi'av,  o{  Chicagi),  has  for  its  objecit  a  moans  whereby  two 
coiinnuiiieations  may  be  simultaneously  transmitted  in  the  same 
direction,  or  in  ojipositc  directions,  or,  in  other  words,  to  doulde 
the  capacity  of  a  Morse  circuit,  having  thereon  several  inter- 
mediate stations,  so  arranged  that  while  a  communication  is 
being  transmitted  from  one  terminal  station  to  the  other  by 
means  of  the  telephonic  system,  cither  terminal  station  or  any 
way  station,  may  at  the  same  time  rc.'Ceive  a  message  fmrn  oi' 
transmit  one  to  I'ither  of  the  terminal,  or  any  one  of  the  way 
olliees  by  means  of  the  ordinary  Morse  apparatus.  This  inven- 
tion has  been  subjected  to  a  series  of  tests  upon  the  lines  of  the 
Western  Ilnicm  Telegraph  Company,  with  considerable  success. 

One  of  the  several  circuits  ujion  which  the  system  was  testeil 
experimentally  extends  from  Chicago  to  Duliu(pic — a  distance 
of  iS-J:  miles — -with  seventeen  intermeiliate  stations  in  the  cir- 
cuit, the  tot;d  conductivity  resistance  of  which,  including  all  of 
the  relays  on  the  line,  being  about  5,000  ohms. 

The  principle  and  mode  of  operation  of  this  invention  is  shown 
in  fig.  79,  -which  represents  the  instruments,  in  connection  with 
th(>  lini',  at  a  terminal  station,  including  l)oth  the  telephonic,  or 
electro-harmonic,  and  the  ordinary  Morse  apparatus,  the  former 
C(msisting  of  transmitter  T,  key  K,  local  batteries  c,  e^  anil  e^, 
vibrator  (jr  reed  V^  receiving  instrument  or  analyzer  A,  rejicat- 
ing  relay  A  1,  sounder  S,  rheostat  11'  and  main  battery  B ;  and 
the  latter  consisting  of  relay  l>.  sounder  S',  kt'v  K',  rneostat  R 
and  condeiiser  C,  the  earth  terminal  of  the  line  being  at  (i.  Kacli 
intermedi;ite  olVice  is  enjiip))ed  with  the  Mor.se  api)aratus  only, 
including  the  condenser  and  rheostat  last  mentioned:  while  at 
the    distant    terminal    station   both    the    telephonic,    or   eli'ctro- 


'  Alistrih't  cil'iiii  iirtii'li'  I'npiii  tlir  .Iimriiul  hCiIh'  Aiinrii'MM  Kli'i'tr'n'ul  Souic^ty,  Vul. 
I..  No.  :;,  tiititlc'il,  .V  N'ew  mill  Pnn'tioal  Applii'iitinu  i>i'ihr  Tolci>lioue,  by  Elisliu 
(iniv,  Si'.  J). 


lt)8 


THE    Sl'EAKlNO   TELEI'IIONK. 


liiirm<inic,  and  the  Morsi^  iX|i]iiira1us  air  arraii^c'd  jirfciscly  a-s 
^Oiowu  in  tlic  diagram. 

To  efTect  tlie  objrct  sought,  viz.,  llic  .^-iinultancous  transnii.-J- 
;ion  of  two  coininuiiicatidus  in  tlio  same,  or  in  opposite  directions, 
it  is  (ilivionsly  essential  tliat  sounder  S  (for  example)  sliould 
respond  solely  to  the  movements  of  key  K  and  transmitter  T  of 
tlie  telephonic  apparatus  ;  while  in  like  manner  tlic  sounder  S^, 
which  is  eonnrctcd  with  tlu^  ^forse  instruments  at  the  di.-;tant 
terminal,  and  at  the  several  intermediate  offices,  should  respond 
solely  to  the  movements  of  key  K^. 

The  manner  in  which  this  i.s  accomplished  will  be  understood 
liy  reference  to  the  ligurc,  and  the  following  explanation  thereof. 


Fig.  79. 

Tlie  transmitter  'V.  whi<li  in  jirineiple  is  similar  t(^  that  used 
in  connection  with  the  duplex  and  (piaili'uplex  systems,  is  oper- 
ated hy  means  of  th(^  key  K  and  local  battery  e.  'V\m  auxiliary 
lever  h,  one  end  nf  which  rests  upon  a,  suitable  fulcrum,  whih; 
the  fre<!  end  I'csts  ufton  the  anvil  of  ti-ansniitler  ^1".  sei'ves,  in  con- 
Tiection  with  the  armature  (t  of  the  latter,  to  control  the  local 
circuit  of  sounder  S  in  a  mannei-  and  lor  a  pur|)ose,  to  be  herein- 
after (lescri  bee  I.  The  vibrat'jror  reed  \' (which,  with  the  receiving 
insti'unient  or  anaiyzer  A,  ai'(!  fully  illustrated  and  desei'lbcM]  on 
pages  153  and  1H2)  is  kept  constantly  in  vibration  by  means 
<if  electro-magnets  and  u  local  battery  (not  shown  in  the  ligure), 


GHAY  S   KJ.El  TKO-HAUMOMU  TELElMKiNK. 


169 


LINE 


iunl  is  tuned  to  a  ecrtaiii  ])itcli,  corresponding  to  the  reed  E  of 
tlie  receiving  instrument  or  analyzer  A.  A.  small  secondary 
lever  ?<i,  having  one  end  pivoted,  while  the  other  end  rests  upon 
tlie  free  end  of  the  armature  or  reed  K  of  the  analyzer  A, 
serves  to  control  the  local  circuit  of  the  relay  A',  which  latter, 
in  turn,  operates  the  sounder  S ;  and  when  thusarrange(I  forms  a 
well  known  deviec  J'or  reversing  the  signals  of  lin^  receiving  in- 
strunuMit  A,  in  order  that  they  may  appear  correctly  upo7i  the 


sou  111 


ler  S.     Tl 


10  normal  cDUdi 


ition  of  the.  kev  K^  of  the  M' 


ors(! 


a^^  ^  „ratus  is  closed  as  shown  in  tiie  figure,  in  which  ]>ositii>n  the 
rheostat!?,  is  cut  out  of  the  circuit,  while  that  of  key  K  and 
transniiltcr  T  is()}>eu.      Disregarding  for  the  ]ireHent  the  a]i})ar- 


r.tus  at  the  distant  t 


ernunal 


1111 


several  intermediate  stations,  th 


n 


route  of  the  circuit  may  he  traced  from  tlie  earth  plate  G  to  mai 
battery  15,  hy  wires  1  and  -,  to  the  receiving  instrument  or  ana- 
lyzer A  ;  thence  hy  wire  o  to  rheostat  11',  and  wire  4  to  the  lever 
«  and  spriiiir  s  of  transmitter  'i" ;  tlieuco  hv^  wire  6  to  relay  1> 


lay 


and  key  K^  to  i\w  line.    With  key  Kclo,<ed,  and  the;  consequent 

e  circuit  is  changed 
I)  to  th<>  vihrator 


orieratuin  ol    ti'ansmitter 


ijiei' 


^r,  \] 


le  I'oute  I 


.f  tl 


as 

or 


foil 


ows  :   l''rom  earth  pla 


te  ( i  1 


i\-  wires 


and 


reed  V,  and  wire  "^  to  stop  o  and  spring  s  of  transmitter 


llieiicr 


by 


station,  !is 


wire  5  to  .clay   1>  and  ke\' 
1)1 'f(  ire. 


,-  Ri  to  the  line  ami  di.-tant 


'he  amount  of  resistance  etni' 


loved  in  the  rlieo.-tat  K^  in  ad- 


dition to  tliatof  the  analyzer  A,  should  he  e([ual  to  the  aiiparent 


resistance  causei 


I   hv   the  vilirat 


ion  o 


f  tl 


le  reei 


I   V 


that 


no 


variation  in  the  streiiLi'th  of  llie  cMirreiit  goingto  th(>  line  is  mani- 
fested in  till!  Mors<!  relay  D  when  the  transmitter 'i' is  either  open 
or  elose<l.      Tln!  rheostat   R  should  he  so  ad  justed,  that  wlien  in- 


serted in   the  liiu!  1 


)V  oiK'nm 


L'-  the  kev  K'    it 


wii 


treiiLitli  of  the  current  to  an  e\lent  siillicient  to  cause  the  iirnia- 


dirmnish  tin 
th 


tiire  of  the  Morse  relav  J>  to  a  ield  to  the  force 


if   its  retraetili 


nriug,  thus  opening 


th 


IOC 


al  circuit  of  sounder  S^. 


lie  eo' 


nd( 


C 


eiiser  U  is  arranger 


Wll 


h  oiK!  set  of   its  poles  con 


Ucclt 


to  wire  .)  am 


1  the  other  to  tiie  front 


.f 


;e\- 


Ki    s 


o  as 


to  shunt  the  iclav  1*  and  rheostat  K,  and  thu~,  when  the  kev  is 


170 


THE   SPEAKING   TELEl'IIONE. 


opened  and  tlui  ivsistanco  E  introduced  into  the  circuit,  the  fnll 
diminution  of  the  ciuTont  docs  not  take  jilace  instantaneously, 
but  only  after  an  excecdiuglj  brief  interval  of  tiiue  and  in  a 
gradual  manner  ^vhile  the  condenser  is  charging.  Jiy  this  means 
the  effect  of  a  sudden  change  in  the  curnMit  on  the  receiving  in- 
stnunent  or  analy>^er  A,  whiih  would  tend  to  make  the  latter 
give  a  false  signal,  is  entirely  avoided. 

The  conden.-^cr  C  also  assists  in  maintaining  a  uniform  condi- 
tion of  magnetism  in  the  cores  of  the  Mor.'<e  relay  D,  by  di.s- 
charLnn"  throucrh  the  electromairnet,  during  the  interval  of  time 
between  the  vibrations  or  when  the  potential  is  falling,  and  in 
this  way  tlu^  eO'eets  of  the,  simultaneous  operation  of  the  tele- 
phonic apj)aratus  are  ])ractically  nullified. 

The  auxiliary  lever  h,  whieli  rests  u])on  the  anvil  of  transmit' 
ter  T,  serves  to  {)revent  a  false  signal  being  given  upon  the 
sounder  S,  which  is  .sometimes  an  annoyance  to  the  operator 
.'^ending.  Thc^  sudden  release  of  the  reed  E  from  the  attractive 
force  of  the  magnets  of  analyzer  A  gives  the  lever  i^  a  bound, 
which  produces  a  "  click  "'  upon  sounder  S.  The  xipper  limiting 
stop  of  the  lever  a  of  the  tiansmittcr  T  is  insulated  from  the  an- 
vil, and  tog(;ther  with  the  armature  n  and  auxiliary  h^vcr  i,  forms 
a  portion  of  the  local  circuit  of  sounder  S,  so  that  when  the 
armature  a  .'ipproaches  the  magm^t  T  the  local  circuit  of  sounder 
S  is  broken,  and  when  I'cleaseil  from  magnet  T,  the  f<')rc(^  witli 
which  it  strikes  against  the  upper  limiting  stop  causes  the  lever 
h  to  vibrate  enough  to  compensate  for  the  vibrations  of  the  '  'd 
E  of  the  analyzer  A,  caused  by  the  latter  being  restored  to  is 
pre\ioiis  condition,  thus  prc\'cnting  the  signal  abov(>  men- 
tione(l  being  givi'U  upon  sounder  S  dui'ing  the  o|)er;  >n  of  l<e 
K  and  transmitter  n\  Tiie  slidinLf  wcinht  C  is  t.  ejialate  tiie 
movements  of  lh(>  lever  J>. 

Thus  it  will  III!  uiider.^tood  that  by  a  depression  of  key  iv  and 
the  coiiseipicnt  operation  of  transmitter  n\  tlic  electrical  paLsi- 
tion3  cau.sed  by  tiie  vibrating  reed  V  will  ]iass  to  the  line  find 
operate  the  analyzer  A  and  reed  E  at  the  distant  terminal,  so  as 
to  record   the  <lesireil  signal  uimn  .sounder  S.  without  producing 


PECULIAKITIES   I'K    VIUKATUKY   CUBUE^:TS. 


171 


any  cfToct  upon  the  Morse  instruments  at  the  several  inter- 
laodiate  stations;  while  at  the  same  time,  by  means  of  key  K^ 
and  rheostat  R  and  relay  I),  a  eommnnieation  may  be  trans- 
mitted to,  or  received  from,  any  one  of  two  or  m(;ri;  way  oiiices, 
equipped  with  suitably  arranged  Alorse  instruments. 


I'lIENOMK.NA    AITEXniNT,   TIIR   TIIANSMISSIOX   OF   VIHRATORY 

CUKUEN'TS.  1 

The  vibratory  impulses  used  in  cloctro-telephonie  transmission 
are  attended  Ity  certain  phcnomenu  which  are  not  apj)aront  in 
uidiiiarv  electric  tclcgrupiiy.  Their  p(>culiaritics  seem  to  l)e 
closclv  coniK'ctcd  with  the  short  duration  and  llic  rapid  suc- 
cession of  liu!  single  imjiulses. 

It  is  iiiv  purixK-"  in  this  j)aper  to  give  the  icsnits  of  some 
e.\p(>rimeuts  on  this  subject,  without  :iUenipting  to  ])resent  any 
wcll-(h!fined  theoi'v  in  regard  to  the  molecular  aeliou  wliicli 
takes  place  under  the  conditions  dcscrilicd,  l)Ut  leaving  tlie 
reader  to  make  such  explanation  as  may  l)e  suggeste(l  In'  tlie 
facts  preseiUed. 

Among  the  I'emarkabli'  developnients  atteniling  the  intro- 
<]uction  of  the  telephone  there  is,  jierhaps,  noin'  more  striking 
than  tlie  effect  upon  the  amplitude  of  tiie  recei\-ed  vil)rati()ns 
whicii    follows    a    change    in    the    magn(!tic    condition   of    the 

recei\-iiig   elect  r<i-UKlL;'net. 

\'erv  early  in  the  course  of  my  (>\perinients  in  the  matter 
<if  telegraphicallv  traii>niiltiug  nuisical  and  other  sounds.  1 
<ilisi  rved  that  liettei"  ell'eei.  were  obtaine(l  when  f  ojuTitel 
tlu'ough  a  closed  circuit,  having  a  constant  cunvnt  of  clc'tri'-ltv 
(lowing  through  it,  and  transmitte(l  the  electric  vibrations  l)v 
simply  superposing  them  iipoiL  tliis  constant  current  without 
varving  its  jtower. 

To  deline  mor(>  I'learly  what  I  mean,  [will  <s\yo  an  instance 
in    my  experience    which    occurrcfl    in    the    winter  of  187-4-5. 


1  By  Elisliii  Gray,  So.  D.  Joiirriul  ol'tlu^  Aiiu'ricuii  Eluotrieul  .Sooiuty,  ls7s. 


172 


TIIK   Sl'KAKlNO  XKLKl'IIONE. 


While  oxpoiimcnting  at  Milwaukee,  with  my  electro-harmonic  or 
electrD-acoustie  iiuilti[)lc  tclei^raph  system,  I  had  with  nn' a  set 
uf  my  apparatus  fur  receiving  tuues,  known  us  the  musical  tele- 
plume. 

One  e\ening,  after  the  regular  work  of  the  day  was  closed, 
I  transmitted  a  few  tunes  across  tin.'  street  from  the  telegraph 
olHcc  to  the  Newhall  llouse.  for  the  amusement  of  some  friends. 
Instead  of  using  an  independent  l)atterv,  I  simply  tapped  one 
of  the  n'gulai-  batteries  of  the  North- Western  Telegraph  Com- 
pany, which  contained  tw(j  hundred  cells  of  the  ordinary  gravity 
form,  by  connecting  my  short  line  wire  to  the  l)attery,  twenty 
cells  from  the  ground  end,  without  in  any  way  disturl)ing  the 
other  connections.  This  battery  at  thi;  same  time  supplied 
three  lines,  whii-h  extended  tlii'ough  Wisconsin  in  Aarious  direc- 
tions to  distant  points.  The  few  cells  which  I  employed  did  not 
in  the  least  intei-fcrc!  with  the  ordinary  working  of  the  lines. 

A  number  of  familiar  tuues  were  played  during  the  evening, 
and  I  was  sui'pri.-ed  next  morning  to  learn  from  v;irious  oillee.s 
in  the  State,  through  which  the  three  lines  ran  that  were  supplied 
by  thi^  (•<)mmon  battery,  that  tlic  tunes  played  were  all  rej^ro- 
dueed  a'l'Iiblv  and  distinc'Iv  bv  the  relavs  in  the  various  olHees 
aloiij  the  line.  Some  of  the  operators  being  ignorant  of  the  in- 
vention of  till'  teleplion(>  at  that  time,  were  very  much  amazed  at 
this  new  exhibition  of  the  nnisical  jiowers  of  their  instrument.'- 
and  I  am  told  that  one  gentleman.  si.\t\-  mil(>s  fi'om  Milwaukee, 
closed  his  (jflicr  that  night  much  earlier  than  he  was  acciistonicil 
tf)  do. 

Til.' relation  of  the  insirument  to  the  variou>  i  ircuits  is  shown 
in  the  diagram.  Ilg.  cSO.  K  ami  '  represent  the  l)attei\  of  two 
hundr(>(l  cells  used  to  siipjily  the  three  telegraph  lines  I,,  ex- 
tending through  Wiseoii.-ni.  T  is  a  musical  transmitter  jilae^Ml 
in  the  short  wire  I'unning  tn  tlu!  Newhall  Ifuilse,  and  attac|i(vl 
to  the  l)atterv.  iweutv  cells  from  the  irround  end.  I\  is  a  Moi'se 
Ivcv  :  ]\r  is  the  electro-magnet,  and  U  tlie  armature  "f  the  ido- 
]ihonie  rec'civer  at  tin-  Newhall  House.  Tt-  will  be  ?'eadilv 
observed,  that   ouch  time  the  trauBmitling  vibrator  closed,  the 


ri'XTLlAUrriES   ok   VIUKATOHY    Cl'llItKXr; 


173 


t\V(Mitv  rolls  of  buttory  they  wonlil  ho  sliort  rireuitoil  llirougli  tlio 
I'crcivci'iii  tin'  Nevvliail  llousi;  uiid  ;j:rnuii(l,  thereby  proportion- 
iilelv  (liiiiiiiisliiii"  tlic  i)(»\vcr«>r  the  whole  batterv  and  restoriii"- 
il  again  each  time  thi'  vibrator  opened  the  short  circuit,  thus 
sendiiiLT  a  series  i>[  vibrations  su[)er])(>-;ed  npon  the  uuifi)rni  ciii'- 
rcnt  llowing  from  the  lar;!-er  iiatteiy  throughout  the  lines  su|)- 
jilied  by  it.  1  was  well  ;i\vare  that  twenty  cells  of  this  form  of 
battei'v,  connected  1o  tla-  three  lines  as  shown,  would  not  jiroibK.-e 
sueli  marked  ell'ect  upon  so  many  magnets  and  at  so  great  a  ilis- 
tuneo  ;  and  1  was  naturally  led  to  conclude  that  tlio  one  hundred 
oi' more  c(,'lls  of  the  additional  batterv.  which    were   not   thrown 


3^ 


K 


-.1^ 


P  JT 


T 


Oil 


[£j 


Fig.  80. 


into  aetion  by  the  transmitter,  in  s<ime   way  played  a  part  in  tlie 
niattcr. 

At  a  later  date — I  tliink  in  the  latter  jtart  of  ISTo — I  made 
anotlier  experiment  at  tlio  .same  jilace,  under  the  followuig  cir- 
cumstances: 1  had  be'en  using  a  wire  tw(j  hundred  miles  in 
length.  an<l  was  engngerl  in  transmitting  a  series  of  tones  simul- 
taneouslv  over  the  same  wire  for  the  purpose  of  applving  it  to 
a  system  of  nudtiple  telegraphy.  T  had  lieen  using  one  liun<ired 
cells  of  1>attery.  divided  into  four  sections,  upon  each  (^nd  of  this 
wire,  as  shown  in  mv  patent  for  a  multiple  circuit,  tiled  in  the 
United  States  Patent  Oflicc,  January  27.  1S76,  in  whicli  it  will 


174 


THK   SPKAKiNC    TKl.KI'IIONK. 


II" 


be  observed  lliat  the  batteries  arc  eonnectcd  to  tlie  1\vo  ends  of 
the  lino  in  the  usual  way  for  an  American  Morse  circuit. 

The  two  l)atteries  were  divided  into  four  sections  by  shunt 
wires,  in  each  of  whicli  was  inserted  a  transmitter  or  a  vibrator 
and  a  Moi'sc  key,  wliich  stood  o]icii  cxcc[it  when  uscl  [\'y  trans- 
mitting^ signals  while  the  vibrators  were  in  oiK'raliou.  If  the 
key  belonging  to  any  viljrator  was  depressed,  it  woidd  throw  in 
vibration  iho  section  of  battery  included  in  its  short  or  shunt 
circuit.  l)y  tl:is  arrangement  I  had  as  many  as  eight  I't'ccivei-s 
in  operatiim  simultaneou.sly,  each  receiving  a  tone  dill'ci'ing  in 
pitch  from  the  others,  and  eacii  having  a  vibration  strength  of 
twenty-iive  cells. 

One  CN'cniiig  I  wislird  to  uKdv(^  an  c.vpeiMmcnt  with  one  tone 


Alp'^ll 


K 


X 


im 


Fhj.  81. 


only,  and  for  tliat  purpose  inserted  only  twenty-live;  ci'lls  in  the 
circuit,  leaving  out,  the  other  one  hmi(lr''d  and  scvcuty-rive,  as  it 
did  not  occur  1o  lui;  at  lirst  that  the  battery  c(>lls  It'l't  out  would 
play  any  p;ii1.  in  a  vibration  not,  included  in  the  shunt  wires 
behiiiging  to  their  partictdar  tones.  ,\s  Iweuty-live  cells  were 
all  ihat  were  used  in  transmitting  any  out;  single  tone,  [  sup[)osed 
that  amount  of  battery  Avoidd  be  suilicient  for  tin;  experiment 
that  I  wished  to  try.  Tlic  position  of  the  l)attery  and  instru- 
ment in  relation  to  each  other  is  shown  in  lig.  81.  ¥t  is  a  battery 
of  twenty-live  cells.  'Y  is  tlu;  vihrator  and  K  the  key  inserted  in 
a  sliort  or  shunt  circuit  thrown  around  the  tweiUy-live  cells  of 
Ijattery.  ]\r  R  is  the  telephonic  receiver.  1  was  sin-priscd  at  first 
to  find  that  no  perceptible  effect  covdd  be  felt  ou  the  receiver 


I'SE   OK   Sfl'l'I.JvMKNTAI-    JIA'ITKUIKS. 


.(O 


ilion  tlin  key  -wan  clijsed  and  tlw  batterv  tlirown   into   v 


ti()ii.     Ai'tcr  workinj;  over  it   I'lH'  sumo  time, 


mcli 


liil';l- 


i(l(>i|  thill 


tlicM'C  must  ])0  some  fault  in  thr  connections,   ami   iii-ocefilcd  i( 


test  tl 


10  wires  1)V  insci'tiii'f  a  Morse  relav 


I  li 


luiid   tlu;   cnvMit 


all  I'i.yht,  when  a  recollection  of  my  fnrmer  cxiicrieni'c  can>cd 
nie  to  jilace  in  tin.' circuit,  an  iidditional  liattcry  i)f  one   hundred 


cells,  leaving;  the  \ilii'at<)i'  and  shnnt  wires  a> 


tl 


ie\'  Wel'O    helnre 


arouni 


1   tlie  twcnt\'di\'G  cells  oiilv.     ^I'iie  ari'anL;enii'nt  after  tin 


nlihtioiial  one  hun 


drcd  ceils  were  insertc^l 


diown  in  li,L!'.  S2. 
M  11  is  the  reecivinjf  telephone,  'V  the  lele])lionie  transniittei'.  K 
tlic  Morse  key. 
e  twentvdive  cells. 


]']  represents  one  hundred  cells  of  battery,  and 


Wl 


len  the  key  was  now  closed,  the  receiver  respondc 


d  without 


Ms 


-H- 


[£] 


F,]i.  S2. 


dilRcnlty.  By  inserting  an  additional  ;nnount,  of  liattcry  in  the 
circuit  at  the  recei\ing  end,  the  aniplituile  of  \-iliratiou  on  the 
receiving  reed,  wdiich  was  tiinc(l  in  unison  with  \\\o,  transniitti.'i', 
was  still  greater.  I  lia\(!  vei'ihed  this  cNperiment  at  dilfereuL 
times  sincti  the  alinxe  ilate,  and  on  ddTerent  lines,  \arying  in 
length  up  to  ii\(;  huiidi'cd  miles  and  oxer.  It  will  1)(!  oliser\-ed 
liy  studying  the  diagram  in  fig.  82,  that  the  only  etl'ect  the  vibrator 
could  have  u[)ou  the  circuit,  when  the  key  was  closed,  was  to 
throw  into  vilir.aiou  the  twenty-five  cells  included  in  its  short 
circuit,  ataratecorrcspondingto  the  fundamental  of  the  vibrator. 
It  would  seem  that  no  cll'ect  could  be  had  from  the  one  liundrod 
or  more  additional  cells,  inasmuch  as  they  were  simply  inserted 
in  that  portion  of  the  circuit  which  was  never  broken  or  opened. 


176 


TIIK    Sl'KAKINd    TKI.KI'llONK. 


[ill 


ox('0]it  to  prodnco  !i  porniiinoiit  mngiiotic  offoot  in  tlio  rooeivin.L'- 
iiiii^nn't  corresiioixling  to  its  iMinviit  strength.  In  otlicr  wofds,  if 
till"  mairiiL'tic  cllVct   jirodiwcd  l)y  tlu;  one  hiiii(ln'(l  cells  is  vcjut- 


sriitcil  liv  twc'iil 


V.  tWrlif.  -Ii\i' 


ddiliiiiKil  cflls  wiiiild  iiicfi 


iISC   till 


iniigiictio  otlVct  to  ii  L'ortiiiii  iioint  aluivf  Isventv,  a 


lid  when 


lal 


en 


.fl  it 


won! 


to  twcntv,  but  not  be! 


( p\v. 
Is  is 


rcprcsi  ntcd  hv  ii 


Vf 


ir  the  power  of  tli(5  twcnty-livi" 
wliy  slioiild  it  not  be  exerted  with  ei|iial  |iower  widioiit  the  one 
linndri'il  cells  inserted  in  tlio  ciiTiiil,  as  described?  This  was 
the  probl(Mn,  and.  in  ;i,  ineasnre  it  is  a  prolileni  still,  although  I 
have  satisfied  myself  in  regard  to  certain  fai-ts  wliicli  help  to 
sti'i'nL''tlien  the  theorv  which  1.  then  lu'ld  in  roLi'ai'd  to  the  matter. 


I 


■il  at  that  ti 


-       ^^         i  eonld  aceount  hir  at    least    part   ol    this 

i^fleet,  upon  tla^  theory  that  the  speed  of  the  signal  was  increased 
by  tlie  additional  jjotential  given  by  the  larger  nnnilicr  of  ceil.s. 
Tu  other  words,  the  vidno  of  any  given  <'ell,  or  number  of  cells, 
when  fornung  ])art  of  n  lai'ge  battery,  is  greater,  especially  if 
used  on  long  lines,  than  when  used  alone,  'i'his  theoi'V,  how- 
ever, is  entirely  inadcipnite  to  account  for  the  whole  efTcct,  us 
will  apjH'ar  fi-oni  what  follows. 

Some  very  inti'resting  experiincuits  bearing  npon  tiiis  matter 
were  made  by  mc  while  experimenting  with  the  s|)eaking  lele- 
jihone,  known  as  the  battery  or  snpplemental-nuignet  ti'lephone, 
a  diagram  of  which  i.s  .shown  in  fig.  83. 

In  this  instrument  no  permanent  steel  magnet  is  used  :  nor  is 
there  eonnected  with  it  a  battery  eurrent  llowing  through  the 
main  line.  Insteail  of  a  ])ermanent  steel  magnet,  sueli  as  is  more 
commonly  used  in  S[)eakingtelei)hoi\es,  I  nsed  an  eleeti'o-magnet. 
B.  which  is  held  [lermanently  ehargeil  by  a  local  battery.  The 
electro-magnet  C,  •which  is  ne.xt  to  the;  diaphragm,  and  wdiich 
conne-'ts  with  the  line  and  ground,  and  a  corresponding  magnet 
at  the  other  end  of  the  line,  are  charged  by  induction  from  the 
core  of  the  magnet  B,  which,  as  before  mentioned,  is  charged 
from  the  local  battery. 

Before  a  battery  current  had  been  ])assed  through  the  coils. 
and  while  the  cores  were  perfectly  neutral,  I  madi;  the  following 


MAdNKTIC   CORKS    KOU   'I'ELKl'IIONKH. 


177 


experiuieul :   I  coiiiuH'ted  llw  tclcpbDiics  to  llu;  two  fiuJs  of  tlie 
lino,  !LS  sliowii  ill  li^^'S;{,  ami  put  on  ii,  looul  Imttcry  at  station  No. 


1,  si 


lowii  at  the  I'iLjlit  hand  df  lli 


with  iiia'nict  B  tin 


tl 


niu''h  the  wires 


ha'_'ruiii.  fdiiiH'ctiiiL''  thi' 
4  k       Thr 


iltciy 

local   liattciy  iit  sta- 

I'ur  lh(!  tiiiK!    left 


lion  No.   2,  at  the  left  of  the  diaLfraiii,   was 

iiiiconnt'cted,  so  that  the  core  of  the  inaLniot  B,  and  also  that  of 


were  both   in  a  neutral  state. 


I 


now 


iilai/ed  iii\'  ear  to  tl 


telejihone  at  slutiou  No. 


aiK 


I  ha.l 


my  assistant  speak  in  a 


loud 


tone  into  the  instrument  at  stition 


No.  1, 


win 


ch  liad  the  local 


battery  attached,  and  was  therefore  in  condition  to  transmit  tli 
electrical  vibrations  produ I   bv  the  motions  of  the  diaphra; 


isni 


1 
i 


Cl  B 


H 


1 


n  ic 


m 


p 


H^iH 


La 


Fiy.  s:i. 


acting  inductively  upon  the  then  inaiinctized  electro-magnet  C. 
Although  the  vilirations  were,  passing  through  the  circuit,  and 
consequently  through  the  coils  of  magnet  ( '.  at  station  2,  I  could 
get  no  audilile  eflfect  until  I  jmt  on  tlu^  local  batters'  and  charged 
the  cores  of  tliC  magnet  at  the  receiving  end  of  the  line.  Im- 
mediately after  this  was  done  I  could  hear  every  word  loudly 
and  distinctly,  making  in  all  respects  the  best  telephone  I  have; 
ever  heard,  due  to  the  fact  that  by  tlu;  aid  of  local  batteries  we. 
I  an  make  of  soft  iron  a  much  stronger  magnet  than  can  be  made 
of  steel.  1  then  threw  ofT  the  battery  at  station  2.  when  I  could 
hear  the  won  Is  very  faintly,  and  I  w;is  able  then  to  transmit  \-ery 
faint  sounds,  due  wholly  to  the  residual  charge  left  in  the  iron 
after  the  batterv  was  taken  olT.     It  is  I'asv  to  see  whv  no  sound. 


IMAGE  EVALUATION 
TEST  TARGET  (MT-S) 


4 


/ 


{/ 


u 
-% 


o 


> 


,V4 


MA 


1.0 

Ui%2S     12.5 

1^  1^    12.2 

1-                  lllll^^ 

U 

1.4    |,.6 

I.I 

1.25 

^ 

6" 

► 

V] 


<^ 


/2 


v: 


OMy 


^     #         "^         vV 


V 


^. 


Photograpmc 

Sdences 

Corporation 


23  W2ST  MAIN  STRHT 

WEBSTER,  N.Y.  H580 

(716)  872-4503 


^v 


k\ 


iV 


178 


THE   SPEAKING   TELEPHONE. 


(•ould  bo  transmitted  from  tho  apparaturf  before  it  had  been 
charged  by  the  battery,  because  there  was  neitlier  electricity  nor 
magnetism  present,  nor  had  we  any  of  the  conditions  n(^(;essary 
to  produce  either  of  tliese  jorees  by  sim})ly  speaking  against  the 
diaphragm.  This  was  not  true,  liowever,  of  tlie  No.  1  station, 
because  the  battery  was  connected  and  tlie  magnet  charged.  No 
(h)ubt  tlierc  was  some  effect  produced  upcm  tlic  receiving  magnet, 
for  tlie  electrical  imjmlses  passing  through  the  line  must  have 
been  the  same  wlictiier  the  magnets  at  the  receiving  end  were 
charged  or  in  ii  neutral  condition.  Tliis  one  fact,  however,  was 
prominently  brought  out,  that  in  order  to  make  an  electro-magnet, 
which  is  tlie  receiver  of  rapid  vibrations  (such  as  will  copy  all 
the  motions  made  in  the  air  wlien  an  articulate  word  is  uttered), 
sensitive  to  ;ill  the  chang(\s  necessary  in  receiving  sounds  of 
varying  (piality,  it  must  bo  constantly  charged  by  .some  foreii 
exterior  to  tlie  electrical  vibrations  sent  through  tho  wire  from 
tiic  transmitting  station.  AVc  were  well  aware  that  tliis  condition 
is  unnecessary  where  tho  force  transmitted  is  of  suflicient  magni- 
tude, or  where  the  signals  are  of  .sufliciently  long  duratioa  My 
experiments  k>ad  me  to  tlie  conclusion  that  a  .soft  iron  core  is  far 
more  susceptible  to  the  slight  changes  in  the  electrical  conditions 
of  the  wire  surrounding  it  when  it  is  already  in  a  high  .^tate  of 
magnetic,  tension.  It  is  like  an  individual  who,  in  his  more  calm 
and  unrudled  moments,  may  be  surrounded  by  little  waves  of 
excitement  without  being  ail'eeted  by  them  ;  when  on  the  other 
hand,  if  from  any  cause  whatever,  his  nervous  sy.stem  is  in  a 
state  of  tension,  he  is  readily  ailected  liy  every  di.sturbing 
influence,  however  slight. 

It  will  b(Mii)ticed  that  the  above  observations  were  made  in 
regard  to  I'lectrical  impulses  of  very  short  duration  ;  the  longest 
several  humlrcd  jier  second,  and  tiie  shortest  many  thousand. 

The  explanation  of  the  aliove  results  may  be  j)artly  umlerstood 
when  we  fully  consider  tlu^  elTects  of  the  extra  current  which  is 
induced  in  the  ])riniary  circuit  itself;  (^specially  when  such  cir 
cuit  has  included  in  it  the  coils  of  an  electro-magnet. 

The  lirst  effect  from  a  current  of  electricity  iiassing  around 


HEACTIVK   EFFKCT  OF   INDUCED  CURRENTS. 


179 


tln^  coils  of  an  olectro-mafniot  is  to  <lcv'elop  magnetism  in  its 
poft  iron  core;  l>ut  as  soon  as  the  coro  begins  to  magnetize,  it 
M'ts  up  a  nioMHMitarv  induced  current  in  tlie  ()])posito  direction 
to  the  ])riniary  or  inducing  current,  th<!  effect  of  wliieli  is  to  re- 
tard tlie  charge  in  tlie  lii-st  instance. 

It  has  long  lieen  known  tiiat  tiiis  reactive  effect  of  tiie  induced 
current  is  strongest  at  the  very  licgiiniiiig  of  the  electrical  ex- 
citement;  while  this  effect  is  only  momentary,  its  duration  is 
still  as  great  as  that  of  tlie  longest  vibratory  ])eriod  of  any  of  the 
tones  of  the  voice. 

When  the  magnet  is  ahvady  charged,  tlie  induced  current  is 
far  less  able  to  act  as  an  (Apposing  agent  to  the  flow  of  the  pri- 
ma.ry  impulse.  The  constant  charge  given  to  .an  elect  it /-magnet 
seems  to  have  an  opposite?  (  fTi'ct  upon  the  seecnidary  im])ulse 
from  that  which  it  has  upon  the  jirimary.  For  [  notii^-d  when 
cxjicrimenting  with  the  induction  relay,  that  if  [  charged  the 
primary  coil  with  a  battery  power  of.  say  five,  tlit;  initial  second- 
ary impiilsi;  would  be  far  greater  than  if  I  left  a  constant  charge 
of  fi\'e  in  the  jn'imary  and  suddenly  raised  it  to  ten. 

1  have  thought  that  a  further  po>siblo  explanation  of  this 
phenomenon  may  be  found  on  the  supiiosition  that,  when  the 
molecules  of  the  iron  are  in  a  state  of  magnetic  tension,  that  is 
to  say.  when  they  hnvi'  moved  from  a  neutral  jioiiit  up  to  ;i  given 
position,  there  is  then  K'ss  molecular  inertia  to  overeoine  in  mov- 
ing them  forward.  The  ])riiiciple  here  suggested  finds  an 
analogy  in  the  superior  resonating  (pialities  of  a  sounding-board 
wliicli  is  under  mechauical  tension,  as  compared  with  one  in  a 
neutral  stat(>. 

It  follows  from  the  obscrvaticins  mach)  above,  in  regard  to  the 
resistance  to  the  jiassagc  of  rapid  vilirations  through  a  helix 
having  inserted  in  it  an  iron  core,  that  any  electro-magnet  in- 
serted in  the  circuit  through  which  rapid  \ibrations  are  electri- 
cally transmitted,  will  eitliertotally  absorb  tlu'in  orgreatly  dimin- 
ish their  power.  T!:is  is  found  to  be  true  in  practice,  and  it  was 
Ji  serious  probliMii  how  to  successfully  use  Sj.^.iking  telephones 
u})on  lines  where  mon^  than  two  stations  were  necessary.     In 


180 


THK   SrKAKING   TELEPHONE. 


order  to  be  able  to  call  the  party  with  whom  we  wish  to  comirm 
nicate,  it  is  iiocossary  to  have  bell  inagncis,  or  other  signaling 
a|j|jaratiis  involving  the  use  of  an  electro-magnet,  and  tliese 
magnets  must  be  in  circuit  when  tiie  line  is  not  in  use,  to  be  in 
position  to  receive  a  call  from  any  station  on  the  line.  If  A,  B 
and  C,  have  offices  on  the  same  line,  and  A  should  signal  to  C, 
they  would  both  switch  out  their  bell  magnets  and  switch  in 
their  telephones ;  but  B's  bell  magnet  would  still  remain  in  cir- 
cuit and  act  as  a  resistance  to  the  i)assagc  of  vibrations  over  the 
line.  This  difhculty  is  fully  obviated  by  the;  use  of  a  (condenser, 
which  is  phuted  in  a  branch  circuit  })assing  around  the  bell  mag- 
nets. So  elTectual  is  the  remedy,  that  even  five  or  six  magnets 
may  be  inserted  in  the  line  without  ])eree])til)ly  diminishing  the 
loudness  of  the  tones  over  that  of  u  clear  wirc^  of  the  same 
length.  The  action  of  tlu;  condenser  in  this  case  h.'is  been  to 
some  extent  ex])laiii<'il  in  an  article  ])ublished  in  the  second  num- 
ber of  this  journal. ' 

The  effect  of  a  condenser  on  impulses  of  short  duration  is  just 
the  reverse  of  that  of  an  electro-magnet ;  the  latter  oflering  a 
momentary  opposition  to  the  passage  of  the  impulse  Dy  creating 
a  counter  one,  which  to  a  great  extent  neutralizes  it,  while  the 
former  offers  an  easy  jias.'^age  to  it  .so  long  as  the  condenser  is 
filling,  which  occupies  a  very  short  .space  of  time.  The  de- 
crease in  resistance  effected  by  the  use  of  the  condenser  is  only 
momentary,  and  will  be  of  no  service  whatever  in  prol(mgcd 
signals.  On  the  other  hand,  tlu^  increase  of  I'csiivtimce  cau.sed  by 
the  insertion  of  an  elec'ro-magnct  in  circuit  is  also  momentary, 
and  does  not  act  as  a  retarding  influence,  where  tlic  signal  or  im- 
pulse is  sufficiently  prolonged,  more  than  the  same  amount  of 
any  artificial  resistance. 

I  will  mention  another  ])eculiarity  which  relates  to  the  con- 
struction of  the  speaking  tele{)hone,  with  reference  to  its  ability 
to  a(!curately  reproduce  the  characteristics  of  any  voice  or  any 
sound  that  may  be  transmitted  through  it  or  received  by  it 


i  For  u  degcriptloii  of  tho  applicat'iua  of  thu  ooiidciiitcr,  hco  pugus  80  and  31. 


PR(  T)IiCTION   OF   VOWEIi   SOUNDS. 


181 


It  is  a  well  known  principle  in  acoustics  that  that  clement  of 
sound  which  we  call  quality  or  chanicter  is  detenuined  by  the 
number  of  over-tones  that  accompany  any  given  fundamental, 
and  the  position  that  tlicy  sustain  wiih  reference  to  the  funda- 
mentiil.  For  instance,  a  pure  tone  is  made  by  a  given  number 
of  vibrations  per  second,  its  vibratory  j)eriods  occur  at  equal 
intervals,  and  it  has  no  otlior  tones  accompanying  it,  of  any  pitch 
or  intensity  whatever.  As  a  matter  of  fact,  however,  nearly  all 
tones  are  composite  in  their  character,  and  the  nature  of  their 
composition,  witli  reference  to  number  and  intensity,  determines 
the  character  of  the  composite  tone  as  a  whole. 

An  api)roximatcly  pure  tone  is  obtained  from  a  tuning  fork 
constructed  with  great  care,  mounted  U])on  a  box  whose  cavity 
corresj)onds  accurately  to  the  pitch  of  the  fork  when  the  air 
column  contained  witliin  it  is  thrown  into  vibration.  Wl>en  the 
fork  is  thrown  into  vibration,  the  sound  of  the  vowel  U  will  pro- 
ceed from  tlie  cavity  of  the  box.  Hence,  the  characteristic  of 
the  vowel  U  is  purity  of  tone,  and  may  be  likened  to  one  of  tlie 
positive  colors,  unshaded  by  the  admixture  of  any  other.  On 
the  other  hand,  if  we  add  to  this  pure  tone,  or  the  vowel  U,  a 
tone  whose  vibrations  are  doiil)]e  the  rate  and  very  intense;  also, 
two  more  tones  of  feeble  intensity,  on(!  with  a  rate  three  times 
as  great  as  the  fundamental  or  lowest  tone,  and  the  other  four 
times,  we  shall  have  a  composite  r(\sultant  sound  whose  character 
is  that  of  the  vowel  C).  And  .so  by  varying  the  composition 
with  reference  to  number  and  intensity  of  tones,  we  jiroduce  in 
turn  all  of  the  other  vowel  sounds,  and,  ia  fact,  every  shade  and 
variety  of  audible  exjjression.  Every  change,  however  slight,  in 
any  single  element  of  a  comjiosite  tone,  either  in  amplitude  of 
vibration,  rate  or  relation  to  the  fundamental  tone  in  the  clang  or 
composition,  produces  a  clumge  in  the  quality  of  the  sound  as  a 
whole.  From  this  it  will  be  observed  how  important  it  is  tliat 
the  apparatus  we  use  in  transmitting  and  reproducing  urtieulate 
s})eech  shall  copy  with  the  greatest  accuracy,  both  in  the  trans- 
mission and  reproduction,  all  the  motions  made  in  the  air  by  the 
speaker.     Any  attempt  to  reinforce  the  viljrations,  by  mounting 


182 


THE   8PKAKING  TKLEI'HOXE. 


the  diaphragm  on  resonant  substances,  sucli  as  wood,  ard  over 
hollow  air  cavities,  serves  to  mutilate  the  words  transinittcd,  and 
destroy  the  i)eculiar  characteristics  of  the  sound.  X  few  mo- 
ments study  of  the  laws  of  acoustics  will  suggest  reasons  why 
tliis  is  BO. 

Every  solid  substance  of  a  resonant  character — striking  ex- 
amples of  which  are  wood  and  some  of  the  metals — tends  to  as- 
sume a  fundamental  character  wlien  thrown  into  vibration.  For 
instance,  when  we  striken  a  bell  of  a  given  size,  it  gives  a  clang 
of  the  same  character  at  every  stroke.  If  !he  size  of  the  bell  is 
changed,  the  character  of  the  sound  or  clang  will  change,  so  that 
everything  of  a  solid  or  massive  character  may  be  said  to  be  able 
to  respvmd  more  readily  to  some  toncb  than  otlici-s.  This  char- 
acteristic increases  as  the  body  assumes  the  form  of  a  vil)ratory 
reed  or  tuning  fork,  and  it  diminishes  as  the  body  is  flattened 
into  a  thin  shajie,  and  assumes  the  form  of  u  diaphragm,  so  tliat 
it  ceases  to  vibrate  more  readily  as  a  whole  than  in  its  equal 
parts.  It  has  then  nu^re  of  tlie  characteristics  of  the  air  with 
reference  to  its  ability  to  take  up  simultimeously  all  forms  of 
motion.  If,  then,  the  transmitting  diaphragm  of  a  speaking  telc- 
jihonc  is  so  constructed  an<l  luounted — with  reference  to  what- 
ever device  is  used  to  transform  its  mechanical  movements  into 
electrical  movements  of  the  same  (piality — that  it  copies  accu- 
rately the  mf)tioiis  of  the  air,  it  must  transmit  ])erfectly,  and 
reproduce  at  tlio  receiving  end  the  same  characteristics  of 
sound  that  were  transmitted,  provided  the  receiving  instrument 
is  eipially  ])erfect  in  its  construction,  'i'o  secure  this  result,  even 
after  the  diajihragm  is  as  ])erfect  as  ])ossible  with  reference  to 
size,  thickness  and  (pialityof  material,  it  must  be  so  mounted  as 
not  to  excite  the  r"sonant  fpialities  of  th(!  snrrounding  material 
which  may  be  a  part  of  the  instrument  ^J'o  this  end,  the  instru- 
ment sh<inl(l  be  constructeil,  cs[ieciallv  that  portion  whi<'his  im- 
meiliately  above  and  bchnv  the  diaj)hragin,  of  some  iion-resonant 
nuiterial,  und  the  diaphragm  sliould  be  clamped  at  its  cdi^es  by 
something  in  the  shape  of  a  pad  or  cushion.  ^    The  air  space  ah >ve 


I A  devii-u  origiiiully  BiiffgOHted  by  I'rol'oiisor  A.  E.  Dolljeur. 


KKKECTS    PKOnUOEl)   HV   IIKSOXAXT   DEVICKa 


188 


and  bolow  the  tliaphnigm  should  bo  the  smallest  possible.  On 
tlie  other  hand,  if  the  body  of  the  instrument  is  made  of  wood, 
and  an  air  cavity  of  considerable  size  is  made  under  the  dia- 
phragm, or  if  any  device  is  employed  to  reinforce  the  tones,  the 
effect  will  be  to  mutilate  the  articulation,  and  change  the  char- 
acter of  the  transiid.ted  sounds.  The  reiuson  for  this  will  appear 
very  plain  when  we  consider  the  importance  of  preserving  the 
relations  of  all  the  simple  elements  which  make  up  a  composite 
sound  of  a  g  ■eu  character.  Those  resonant  devices  will  resonate 
or  reinforce  S(  uj  of  the  tones  of  a  clang  and  not  theothei"s,  thus 
throwing  the  c  mjiosition  out  of  proportion,  and  consequently 
destroying  its  character. 

1  In  tlic  following  l)ages,  which  rehite  especially  to  the  tele- 
graphic transmission  of  musical  and  other  sounds,  it  is  my 
(U'sign  to  give,  with  as  much  accuracy  as  possible,  a  concise 
history  of  my  own  experiments  and  observations,  as  they  have 
been  made  from  time  to  time  since  I  Ix'gan  the  investigation  of 
this  subject.  It  is  not  ray  intention  to  enter  into  the  work  which 
h.xs  been  done  by  others;  but  to  furnish  as  faithful  a  record  as 
])()ssil)lo  of  my  own,  leaving  tlie  world  to  judge  who  is  most 
justly  entitled  to  priority  of  invention  and  discovery  in  respect 
to  the  various  things  licreinaftcr  set  forth. 

At  the  tiniewhet>  I  began  my  investigations  in  connection  with 
the  above  sulijcct-mattcr,  I  had  no  knowledge  that  any  one  had 
])rcviously  done  anytliing  in  this  fu'ld.  I  was,  however,  familiar 
with  the  general  fact  wliicli  had  been  made  known  by  Page  and 
Ilenrv,  in  relation  to  the  effect  produced  upon  the  iron  core  of 
an  electro-magnet  at  the  moment  of  its  charge  and  discharge.  I 
also  hud  s  ime  general  idea  of  the  nature  of  the  experiments  of 
Rciss,  of  Germany,  which  were  made  about  the  year  1861,  but 
hail  no  knowledge  at  the  time,  or  until  more  than  a  year  after 
I  h;id  been  actively  engaged  in  telephonic  rescarcli,  that  any  one 
beside  mvself  was  devoting  any  attention  to  the  same  subject. 

A  glance  at  m^'  antecedents  may  not  l)e  inappropriati;  at  this 


AlistriK't  of  Expenrntntal  lie»earcheti,  by  Klislm  finiy,  Si'.  ]). 


181 


THK   SI'KAKINO   TELEPHONE. 


point,  inasmuch  as  it  will  help  to  show  how  I  came  to  be  led 
into  this  particuhar  field  of  physical  research. 

Frona  my  earliest  recollection  I  was  profoundly  interested  in 
all  the  phenomena  of  nature,  and  had  an  intense  desire,  whenever 
I  saw  any  manifestation  of  physical  force,  to  become  acquainted 
with  the  secret  of  its  operation.  WIkmi  I  saw  a  piece  of  ma- 
chinery of  any  character  whatsoever,  I  usually  attempted  to  re- 
produce it  Of  course  I  was  unsuccessful  in  most  instances,  owing 
to  the  fact  that  my  facilities  for  constructing  machines  were  very 
limited,  and  my  exi)erience  as  a  mechanician  at  that  early  age 
was  meagre.  However,  not  all  of  my  attempts  were  failures ;  for, 
I  have  in  my  mind  the  memory  of  the  ojieration  of  many  ma- 
chines constructed  by  my  own  hands,  ranging  from  a  saw-mill 
run  by  water  power  to  a  Morse  telegraphic  appai-atus. 

Among  all  the  phenomena  throughout  the  domain  of  physics, 
nothing  took  such  hold  upon  my  mind  as  that  exhibited  in  the 
various  effects  produced  by  the  action  of  electricity.  I  read 
whatever  I  could  finil  relating  to  this  subject,  with  the  same 
eagerness  and  interest  that  most  boys  would  read  Robinson 
Crusoe  or  the  Arabian  Nights  ;  and  many  were  the  scoldings — 
to  say  nothing  of  stronger  appeals  that  were  sometimes  made — 
that  I  received  in  consequence  of  my  enthusiasm  in  experi- 
mental investigations  in  the  various  branches  of  physics.  As  I 
look  back  from  this  jioint,  however,  I  feel  no  disposition  to  com- 
plain of  what  I  then  not  unnaturally  regarded  s^;;  harsh  treat- 
ment; for  I  can  readily  sec  that  it  was  not  altogether  ])leasant 
for  my  mother  to  find,  as  she  sometimes  did,  that  whole  skeins  of 
flaxen  threail,  which  she  had  s))un  with  her  own  fingers,  had 
been  used  u])  in  manufacturing  belts  to  d.'ive  machinery  which 
in  her  eyes  promised  very  small  rcsidts;  or  to  discover  that  her 
best  ease-knife  had  been  notched  into  saw-teeth,  with  which  to 
equip  a  miniature  saw-mill.  Neither  was  it  altogether  agreeable 
to  her  feelings  to  find  her  only  quart  bottle — for  quart  bottles 
in  those  days  were  rare,  and  highly  prized  by  t\w  housewife 
— converted  into  a  cylinder  for  anelectrical  machine  ;  or  to  have 
the  copper  bottom  of  her  wash-boiler  cut  up  to  make  the  plates 


GKAVS  EARLY   EXPERIMENTS. 


186 


of  a  galvanic  pile.  I  even  think  I  wonlcl  have  invaded  the 
sacred  precincts  of  her  l)aiidbox,  which  wa-s  only  opened  once 
a  week,  if  thereby  I  could  have  made  its  contents  subserve  a 
pui^iose  in  connection  with  any  of  my  boyisli  schemes. 

While  yet  a  boy  I  constructed  a  Morse  register,  all  the  j)arte 
of  which  were  made  of  wood,  with  the  exception  of  the  magnet, 
armature  and  embossing  point  in  the  end  of  the  lover  (which 
latter  I  made  by  filing  a  nail  down  to  a  point).  I  had  the  magnet 
bent  into  a  U  form  by  a  blacksmith,  and  then  wound  it  with 
brass  bell-wire,  which  was  insulated  with  strips  of  cotton  cloth 
wrapped  anjund  it  by  hand.  For  a  battery  I  made  use  of  a 
candy  jar,  in  which  I  placed  coils  of  sheet  copper  and  zinc,  with 
a  solution  of  blue  vitriol.  "With  these  materials  I  succeeded  in 
making  a  very  good  electro-magnet,  which  would  sustain  nearly 
a  pound  weight,  and  which,  when  mounted  as  a  part  of  the  instru- 
ment, performed  tlio  work  of  actuating  the  armature  with  per- 
fect success. 

At  quite  an  early  age  I  was  apprenticed  to  a  blacksmith,  and 
worked  with  him  at  that  business  about  one  year.  Some  of  the 
edge  tools  which  I  made  daring  that  time  are  still  in  my  mother's 
possession.  I  soon  found,  however,  that  this  business  was  too 
laborious  for  me,  as  I  was  naturally  of  a  rather  frail  constitution. 
I  therefore  relinepiishcd  it,  and  biicame  an  apprentice  to  a  car- 
penter, joiner  and  boat-builder.  I  served  a  full  apprenticeship, 
during  which  time  I  was  employed  in  almost  every  department 
of  wood-work. 

The  prime  motive  which  actuated  me  tlirough  all  these  years 
tliat  I  had  worked  at  the  bench  was  my  tliirst  for  knowledge. 
I  felt  sure  that,  with  my  trade  as  my  capital,  I  could  work  my 
v.'ay  through  a  course  of  study.  In  pursuance  of  this  idea, 
the  time  having  expired  for  which  I  had  apprenticed  myself 
(three  years  and  a  half),  I  began  a  regular  course  of  study,  while 
by  working  a  portion  of  each  day  and  during  vacation  at  my 
trade,  I  was  enabled  to  pay  my  necessary  expenses  and  keep  up 
with  n\y  class.  Here,  as  everywhere  else,  the  capacity  and  ability 
to  master  everything  relating  to  physical  .><cicnce  was  perhaps 


186 


THE  SI'KAKING  TELEPHONE. 


the  most  prnminont  characteristic  exhibited  during  my  collegiate 
course.  While  studying  natural  philosophy,  it  was  my  custom  to 
make  and  carry  with  me  into  the  class  such  apparatus  as  could  be 
readily  constructed  and  would  ser\e  to  illustrate  the  lesson.  My 
habit  of  actually  constructing  everything  which  I  saw  or  read  of, 
so  far  as  my  facilities  would  allow,  was  the  best  possible  method 
of  fixing  the  j)riiiciplcs  of  its  operation  firmly  in  my  mind. 

1  have  given  tliis  short  autobiographical  sketch  simply  to  show 
the  natural  bent  of  my  mind,  and  the  characteristics  which  have 
been  most  prominent  throughout  my  life. 

My  career  as  a  professional  electrician  and  inventor  dates  from 
the  year  1866,  since  which  time  I  have  invented  numerous 
'^Ui'trical  appliances,  mostly  relating  to  telegraj)hy.  Some  of 
have  gone  into  general  use,  but  only  a  j)ortioii  of  them  have 
.  secured  by  lettci's  patent.  My  time  has  been  wholly  oc- 
cupied in  the  prosecution  of  electrical  investigations  and  in- 
ventions, with  tlic  exception  of  that  which  has  l)een  rc(juir('d  to 
secure  and  exploit  certain  of  these  inventions,  and  that  which 
has  been  devoted  to  the  science  of  acoustics,  in  connection  with 
the  telephone. 

My  lirst  ])atent  for  electrical  or  telegraphic  apparatus  wa.^ 
granted  October  1,  1867.  Since  that  I  have  made  a  consider- 
able number  of  clectriciil  inventions,  many  of  which  have  been 
patented.  Including  cases  now  pending,  the  number  amounts  t() 
about  forty  in  this  country  and  thirty  in  foreign  countries. 
Thirty  of  the  United  States  cases  and  twenty-five  of  the  foreign 
relate  to  the  harmonie  telegraj)li  or  tele])hone. 

Fig.  8-4  shows  the  arrangement  of  the  circuits  and  position  of 
the  <»|)erator  when  the  bath-tub  experiment  was  made,  which  is 
described  on  i)age  151. 

This  experiment  produced  a  profound  inij>ression  upon  my 
mind,  and  dcterniini'd  me  at  once  to  take  the  matter  up  in 
earnest  and  see  what  might  bi'  in  it. 

I  procured  a  violin,  and  taking  off  the  strings,  sukstituted  in 
their  jilace  a  thin  metal  plate  j)rovitled  with  a  wire  connection, 
so  that  I  could  attach  it  to  one  pole  of  the  induction  coil  or  bat- 


( 

III 


fiij 


HATH-Tl" »   KX I'KIUMKNT. 


187 


n  of 
•h  is 


3d  in 


Fig.  84. 


188 


THE  SPEAKING  TELEPHONE. 


tery,  tliuH  ])lafiii^'  it  in  tlio  aiiu'  position,  witli  reference  to  ilie 
body,  that  tlic  ])atli-tiil)  was  in  the  original  exj)criment.  By 
nibbing  the  plato  in  tlic  same  manner  as  before  described,  the 
sound  of  the  electrotome  was  reproduced,  acconipanicd  by  tlic 
peculiar  quality  or  timbre  bclongitig  to  the  violin.  1  noticed, 
however,  tliat  the  characteristics  of  the  initial  vibrations  were 
faithfully  preserved,  and  all  that  was  needed  was  to  sift  out  rucU 
foreign  vibration."?  as  w  o  c.\cite«l  in  the  receiver,  owing  to  its 
peculiar  construction ;  i'<  which  case  there  would  remain  the  exact 
cluiractc'- — nothing  more  nor  nothing  less — of  the  transmitted 


Fiij.  85. 

vibrations.    Fig.  85  shows  the  violin  and  the  manner  of  holding 
it  when  in  operation. 

I  subsequently  .sukstitutod  for  the  animal-tissue  receiver  an 
electro-magnet  conibinccl  with  a  hollow  box  of  tiinied  iron,  hav- 
ing an  opening  in  one  side,  whih;  the  oth(>r  was  held  over  th(! 
poles  of  the  magnet  at  such  a  distance  from  it  as  would  iiroduce 
the  best  effect. 


TKANSMISSION   OK   OOMI'OSITK   TONKs. 


189 


With  this  nppiinitus  I  noticed  tlwit  when  I  dejircssed  two  keys 
on  my  tmnsmitter,  it  tlies(>  v/viv  in  tlic  j)ropcr  rohition  to  cai'li 
otlicr,  !i  coniposite  tone  would  bo  received,  tIniH  deinonstrutiiig 
tlio  jfeneral  fact,  tlmt  with  ii  receiver  properly  coustnicted  and 
a  transuiitter  properly  niadc;  and  arrange<l  in  the  eirer*  oni- 
\nmic  tones  of  varying  quulity  could  be  transmitted  and  rct:i\  >  ^1 
telegraphically.  This  apparatus  is  shown  in  fig.  86.  In  hot'i  of 
these  cases  I  u.^ed  an  induction  coil,  placing  the  tranynii iters  in 
the  primary,  while  the  line  was  connected  to  the  secondary  coil. 

The  aliove  fact  respecting  composite  tones  was  more  strongl  v' 
impressed  upon  my  mind  when  I  completed  my  musical  traus- 


-^Itittlt  'j; 


Fi'j.  86. 

mittcr,  having  a  scries  of  tuned  reeds  corresponding  to  the  dia- 
tonic scale.     This  instrument  is  sliown  in  iig.  87. 

When  the  fact  dawned  upon  me,  and  liad  l)een  confirmed  by 
demonstration,  that  sounds  of  a  composite  character  could  be 
transmitted  through  a  telegraphic  circuit  and  reproduced  at  the 
receiving  end,  and  the  possibilities  of  the  invention  and  the  great 
results  to  which  it  must  eventually  lead  ]iassed  through  my 
mind,  I  at  once  foresaw  so  many  possible  ap])lications  of  it 
that  it  became  a  serious  question  which  line  of  investigation  to 
lirst  pursue. 

Among  other  conceptions  of  the  probabilities  of  the  invention 


190 


THE   SPEAKING    TELEPHONE. 


■was  that,  at  an  early  day,  not  only  musical  compositions  of  a 
complicated  character,  but  oven  articulate  speech  would  he  trans- 
mitted through  a  single  telegraph  wire. 

In  addition  to  this,  I  could  plainly  sec,  also,  how  that  musical 
tones,  dillering  in  pitch,  could  bo  siiuultancously  transmitted 
throufTh  the  wire  and  analyzed  at  the  receiving  end,  so  that  a 
transmitter  and  a  I'eceiver  corrt'spoudiiigly  tuned  would  trans- 
mit and  receive  a  tone  corresponding  to  their  own  ])itch.  reject- 
ing all  others  ;  while  at  the  same  time  a  number  of  other  tones 


Fig.  87. 

differing  in  pitch  might  be  simultaneously  transmitted  and  re- 
ceived through  the  same  wire. 

In  truth,  the  general  fact  had  already  been  demonstrated,  but 
thc'c  was  still  needed  that  perfection  in  the  details  of  apparatus 
and  arrangement  of  circuits  which'  were  essential  to  success. 

Another  conception  which  c^-'uried  to  me  at  this  time  was 
that  of  applying  the  invention  to  a  printing  tel(>graph,  so  that 
each  type  would  be  actuated  by  a  tone  of  a  jiarticular  pitch. 

Having  all  these  uses  in  my  mind,  and  supposing  I  had 
seciu'eil  in  my  lirst  patent  the  fundamental  principles  that  would 
underlie  all  the  various  applications  that  might  bo  made  in  the 


VARIOUS   FOKMS   OF  TUANSMirriNU   REEDS. 


191 


matter  of  transmitting  sounds  telograpliically,  I  pursued  m\- 
investigations  in  a  systematic  way,  placing  each  development  to 
tlie  credit  of  the  jiarticular  application  to  which  it  seemed  to 
belong. 

Being  well  conversant  with  the  facts,  so  far  as  they  were 
then  known  in  the  sciences  of  electricity  and  magnetism,  I  was 
fully  prc[)arcd  to  avail  myself  of  what  had  already  been  done  in 
that  line.  I  was  not,  however,  experimentally  conversant  to 
the  same  extent  with  the  facts  in  the  science  of  acoustics,  but 
theoretically  the  subject  was  a  familiar  one  to  me.  I  devoted 
eonsiderable  time  to  familiarizing  myself  experimentally  with 
that  science,  es^  'cially  that  branch  which  related  to  the  (pialities 
of  composite  tones  ;  so  that  I  was  able  to  give  the  composition  of 
the  various  vowel  sounds,  and  determine  in  general  the  relation 
between  the  character  of  a  sound  as  it  seemc(l  to  the  hearer  and 
the  physical  fact  as  it  existed  in  the  form  of  motion,  cither  in  the 
air  or  any  medium  through  which  it  was  pi'0])agated.  In  this 
connection  I  madt^  a  number  of  experiments  having  reference  to 
the  transmission  of  sounds  varying  in  iiuality. 

I  devoted  myself  principally  to  the  construction  of  various  de- 
vices for  transmitting  musical  tones  telegraphically,  for  this 
seemed  to  be  the  lirst  fundamental  .step  to  take  in  the  direction, 
either  of  musical  or  of  multiple  telegrapliy. 

I  accordingly  experimented  with  various  forms  of  transmitting 
reeds,  one  of  which  consisted  of  an  ordinary  electro-magnet  and 
a  reed  made  of  a  ])iece  of  watch-spring,  one  end  <  "  Inch  was 
fixed  to  one  pole  of  the  magnet,  while  the  other  or  free  end 
projected  ovr  the  other  pole,  a  short  distance  from  it,  so  as  to 
form  an  arniaturc. 

The  circuil:  which  actuated  this  reed,  after  passing  from  one 
pole  of  the  battcrv  through  the  helix,  was  cotmected  to  the 
magnet  cores,  thereby  making  the  reed  a  part  of  the  circuit,  the 
pole  being  connected  to  a  ])oint  r(\sting  against  the  reed  one 
third  of  the  distance  from  its  lixed  to  its  free  end. 

The  transmitting  reed  above  describe<l.  when  adjusted  very  ac- 
curately, will  give  a  musical  tone  of  givat  purity  ;  but  the  slightest 


192 


TUE   SPEAKING  TELEPHONE. 


change  iii  the  adjustment,  even  ajar  of  tlic  table,  eauscs  it  to  break 
into  nodes,  and  give  a  note  a  tliird  or  an  octave  away  from  its 
fundamental.  It  was  evident  to  my  mind  that  there  were  inher- 
ent difficulties  iu  the  use  oi  this  form  of  reed  which  would  render 


Fig.  88. 

it  impracticable  for  regular  service.  In  the  fii"st  place,  it  was  too 
flexible  throughout  its  whole  length,  partaking  largely  of  the 
properties  of  a  thiu  diaphragm,  and  thcrebv  r(>sponding  too 
readily  to  the  harmonics  of  its  fuudamentid.     Another  ilifficulty 


Fig.  89.      . 

was,  that  the  free  motion  of  the  reed  was  impeded  by  its  com- 
ing in  contiict  with  the  break-point,  where  the  current  is  inter- 
ru{)ted. 

To  obviate  the  first  objection,  a  reed  was  made  of  heavier 
material,  and  tuned  by  filing  it  at  one  point,  near  its  li.xed 
end,  as  shown  in  fig.  88.     To  obviate  the  second  objection — the 


VARIOUS   FORMS   OF  TELEPHONIC   RECEIVERS. 


193 


solid  contact  between  tlie  reed  and  })reak-point— a  short  and 
thin  intermediate  spring  was  mounted  upon  the  reed,  the  free  end 
of  which  came  in  contact  with  the  break-point.  This  inter- 
mediate spring  is  shown  in  lig.  89. 

Several  fortiis  of  receivers  invented  by  me  have  been  alreadv 
described.     Another  form  is  shown  in  tig.  <J0. 

This  consisted  of  a  sheet  of  silver-foil  paper  stretched  upon  a 
metal  hoop  about  four  inches  in  diameter,  like  a  tambourine, 
terminating  in  an  insuhited  liandlc.  Attaching  the  line  to  this 
hoop,  by  a  connection  which  ran  through  the  handle,  and  grasp- 


Fig.  90. 

ing  the  ground  or  return  wire  with  one  hand,  at  the  same  time 
holding  llie  |.;i]HT  (Inim  with  the  other,  tlie  tune  would  be 
amlible  not  only  to  tiie  one  holding  it,  but  to  othei-s  near  by. 
This  I  discovered  to  be  wholly  due  to  spark  action,  and  not  to 
be  i'ceounted  for  on  the  same  principle  as  when  the  naked 
plate  and  rubbing  were  employed. 

Another  form  of  njceiver  is  shown  in  fig.  91. 

It  consists  of  an  iron  pan  moimted  upon  a  wooden  base,  and 
supported  by  the  standard,  which  is  firmly  secured  to  the  base 


194 


THE   SPEAKIN'(}   TKLEPHONK. 


ami  the  rim  of  tlio  iron  pan.  The  bottom  of  tlic  pan  I  used  as  a 
diapliragm  for  the  iveoiver  of  musical  and  otiior  sounds;  and  the 
rim  answered  as  a  frame  in  wliich  the  (Uajjiii-agm  was  held  in 
]K>siti()M.  Upon  another  standard,  mounted  on  the  same  base 
and  ni'ar  to  it,  was  tixed  an  electro-magnet  whose  poles  projected 
into  the  ])an,  and  nearly,  but  not  (piite,  touching  its  bottom.  By 
means  of  a  screw  between  the  two  standards,  T  was  enabled  to 
secure  the  proper  position  of  the  magnet  with  reference  to  the 


Fig.  91. 

diaphragm.  I  sometimes  used  a  sui^plemcntary  brace  (not 
shown),  which  rested  against  tlie  top  of  the  rim,  as  an  additional 
means  of  more  rigidly  holding  the  diaphragm  in  jwsition. 

"^riiis  instrument  I  used  in  connection  with  various  transmitters, 
especially  with  tlie  one  shown  at  fig.  87,  and  was  the  -osult  of 
a  series  of  experiments  with  thin  iron  and  steel  plates  mounted 
over  the  poles  of  an  electro-magnet.  This  I  found  to  be  a  con- 
venient way  of  mounting  thin  plates.     It  will  be  observed  that 


VAKIOUS   FORMS   OK   TELEPHONIC   RECEIVERS. 


195 


this  instrument  embraces  all  the  substantial  features  in  the  ine- 
clianical  construction  of  the  speaking  telephone  of  to-day.  When 
used  in  connection  with  my  articulating  transmitter,  articulate 
words  have  l)ecn  received  ujton  it,  and  when  a  duplicate  of  the 
instrument  is  inserted  in  a  closed  circuit,  which  includes  a  gal- 
vanic battery,  it  becomes  a  speaking  telephone  capable  of  acting 
both  as  a  transmitter  and  as  a  receiver. 

I  designed  another  method  of  transmitting,  which  I  called 
the  organ-pipe  transmitter,  shown  in  lig.  92.  The  drawing 
shows  a  top  and  a  side  view  of  an  ordinary  organ  pipe,  with 
a  space  cut  away  at  the  centre,   in  length   about  equal   to 


Fig.  92. 

the  width  of  the  pipe,  and  in  depth  just  the  thickness  of  the 
■wa  .  .  the  pipe,  making  an  opening  which  was  covered  with 
a  thin  diaphragm  h.  A  screw  I),  provided  with  a  ))latinum 
point  projccing  through  a  mcfal  brace  d  secured  to  the  side  of 
the  pii>e,  was  adjusted  very  !>ear  to  the  diaphragm  h.  The  latter 
had  glued  to  it  a  thin  piece  of  platinum,  to  which  was  connected  a 
small  wire  c,  terminating  in  a  binding  post  C. 

It  is  a  peculiarity  of  an  organ-pipe  with  an  open  end,  that 
when  its  fundamental  note  is  sounded  the  waves  are  con- 
densed most  powerfully  in  a  lateral  direction  in  its  centre.  I 
took  advantage  of  this  fact  to  profluce  a  vibration  in  the  dia- 


196 


THE  SPKAKINO   TKLKl'IIONE. 


phragm  b,  which  would  make  contact  at  each  movement  with  the 
screw  D.  As  the  condensations  and  rarefactions  of  the  air  in  the 
tube  were  synchronous  with  the  vibrations  necessary  to  produce 
a  tone  corresponding  to  the  fundamental  of  tlic  pipe,  it  is  j^lain 
that  the  movement  of  the  diapliragm  would  be  the  same.  By  con- 
necting a  battery  and  receiving  instrument  through  the  bind- 
ing posts  and  the  point  D,  when  the  organ-^jipe  is  sounded 
its  proper  tone  will  be  produced  on  the  receiving  instrument  by 
electro-magnetic  action. 


Fig.  93. 

I  made  a  scries  of  these  transmitters,  operating  them  with  a 
bellows,  and  when  worked  with  uniform  pressure  of  air,  they 
produced  splendid  results.  In  fact,  it  mckcs  a  very  good  form  of 
transmitter,  and  other  things  being  equal,  would  be  quite  as  good 
as  the  one  we  have  most  generally  used  This  method  of  trans- 
mission, however,  involves  the  employment  of  a  bellows,  pro- 
vided with  some  attachment  for  maintiiining  a  uniform  pressure, 
as  well  as  with  power  to  work  it;  so  that  it  seemed,  at  least  for 
t(',legraj)liio  purposes,  that  some  form  of  transmitter  having 
electricity  for  its  motive  power  would  be  more  appropriate.     I 


TELEPHONIC  TRANSMITTERS. 


197 


nth  the 
r  in  the 
produce 
is  plain 
By  con- 
ic bind- 
sounded 
tnent  by 


therefore  continued  to  prosecute  my  experiments  in  that  direc- 
tion. 

In  order  to  diminish  the  number  of  magnets  in  a  transmitter 
having  a  large  number  of  reeds  differently  tuned,  I  designed  a 
compound  magnet,  as  shown  at  fig.  93. 

This  consisted  of  two  ordinary  electro-magnets,  with  their  poles 
far  enough  apart  to  give  the  proper  length  to  the  reeds.  I  con- 
nected the  positive  pole  of  each  to  the  ends  of  a  bar  of  soft  iron 
about  eighteen  inches  in  length,  and  the  negative  pole  to  a  similar 
bar,  so  that  when  the  magnets  were  charged  one  bar  would  show 


m  with  a 
air,  they 
)d  form  of 
te  as  good 
i  of  trans- 
lows,  pro- 
1  pressure, 
t least  for 
[;r  having 
ipriatt;.     I 


Fig.  94. 

positive  or  north  polarity  and  the  other  south.  The  magnetism 
was  about  equally  distributeil  through  the  length  of  each  bar. 
This  arrangement  enabled  me  to  get  a  large  number  of  reeds 
upon  a  small  number  of  magnets.  I  found,  however,  that  the 
power  was  too  much  distributed  to  produce  good  results  upon 
any  single  reed,  without  increasing  the  battery  to  an  undesirable 
extent,  so  I  abandoned  this  form  and  subsequently  constructed 
the  one  shown  in  fig.  94. 

This  is  substantially  the  same  as  my  transmitter  shown  in  fig. 


198 


TJIK   Sl'KAKINU   TKLEIMIONK. 


87,  exoopt  tliat  I  use  two  and  three  reeds  upon  eaeli  magnet,  all 
diiTcrently  tuned. 

Another  furin  of  transmitter  invented  by  me  is  sliown  in 
iig.  95. 

It  consi.sted  of  a  revolving  shaft,  upon  which,  were  inomitcd 
two  eccentric  cams,  having  one  or  more  jirojections.  These 
actuated  two  small  levers,  causing  them  to  vibrate  ujton  their 
respective  break-points,  through  which  points  a  battery  current 
passed.  From  a  ])ulley  on  this  shaft  I  connected  a  belt  to  one 
of  the  wheels  of  a  lathe  which  was  driven  by  steam  power,  from 
which  it  deriveil  a  uniform  motion  and  a  dclinite  rale  of  speed. 


Fig.  95. 

I  refer  to  my  experiments  with  this  particular  apparatus 
because,  although  simple  in  themselves,  they  were  the  means  of 
giving  my  mind  a  new  impulse  in  another  direction,  and  one 
which  soon  conducted  mo  to  the  solution  of  the  problem  in- 
volved in  the  transmission  of  articulate  words.  I  employed,  in 
connection  with  this  transmitter,  one  of  my  common  receivers 
which  was  adapted  to  the  reception  of  all  varieties  of  sounda 
The  pressure  of  the  levers  upon  their  contact-points  was  con- 
trolled by  elastic  springs. 

When  this  apparatus  was  put  in  operation  I  noticed  that  a 


1i 


TRANSMISSION   OF   AKTICULATE   SPEECH. 


109 


tJciiiiid  of  peculiar  quality,  not  vnilike  that  of  tlio  huinan  voice 
wlicn  in  great  distress,  j)rocuedcd  from  the  receiver. 

By  altering  the  tension  of  the  spring  in  various  ways  with  my 
hand,  I  found  that  I  was  able  to  imitate  many  different  sounds, 
involving  the  vowels  only.  I  succeeded,  among  other  things,  in 
producing  a  groan,  with  all  its  inflections  in  the  greatest  2)erfection. 
By  skilfully  manipulating  the  sjjring  in  the  manner  before  men- 
tioned, a  very  great]  range  in  the  quality  of  the  sounds  was  pro- 
duced, using  only  a  single  break-point 


Fig.  9G. 

Up  to  the  time  of  making  this  experiment  I  had  associated  in 
my  mind,  in  connection  with  transmission  of  spoken  words,  a 
complicated  mechanism  involving  a  separate  vibrating  reed  for 
each  separate  tone  transmitted.  This  experiment  jiroduced  an 
entire  change  in  my  views,  and  I  canio  to  the  conclusion,  that  "', 
could  alllie  done  l)y  means  of  a  single  transmitter;  although,  at 
that  time,  I  did  not  carry  my  experiments  farther  in  that  direc- 
tion, being  too  much  absorbed  in  my  multiple  telegraph  scheme. 

During  the  latter  part  of  the  spring  and  early  part  of  the  sum- 


200 


THK   SPEAKINO  TELEPHONE. 


mcr  of  1875,  I  wm  engaged  in  coiistnieting  iiml  ii(la[)tiiig  my 
system  to  a  type-printing  telegraj)!!,  au  idea  whirh  I  had  con- 
ceived early  in  1874  I  had  it  rodiieed  to  practice  far  enough  to 
demonstrate  the  applicaliility  of  tlio  principles  involved.  la 
January  or  February,  1875,  I  constructed  an  operative  machine, 
at  that  tiineliaving  three  letters  of  the  alphabet,  together  with  the 
mechanism  for  controlling  the  printing  and  moving  the  paper. 
An  outline  view  of  this  machine  is  shown  in  ligs.  96  and  97. 

The  model  of  this  machine  was  completed  and  forwarded  to 
the  Patent  Office  in  October,  1875.     The  y)atent  on  it  was  issued 


Fig.  97. 

July  4th,  1876,  to  which  I  refer  for  a  complete  description.  The 
general  principle  of  operation  may  be  briefly  stated  as  follows  : 
A  particular  tone  actuates  each  particular  type,  so  that  there  is 
a  transmitting  vibrator  and  corresponding  receiver  for  each  tone. 
A  simple  touch  of  a  key  j^rints  the  letter  at  the  receiving  end 
without  the  necessity  of  waiting  for  a  type-wheel  to  come  into 
position.  The  printing  is  executed  upon  a  sheet  instead  of  a 
long  strij)  or  ribbon,  as  in  the  ordinary  step-by-step  machine.  It 
will  not  b{;  necessaiy  to  describe  the  mechanism  iii  detail  in  this 
place,  as  it  is  fully  .set  forth  in  the  specification  of  the  patent  itself. 


INVENTION   OP  THE   SPEAKIN(}   TELEPHONE. 


201 


During  a  visit  to  Milwaukoc  I  saw  for  the  first  time  a  toy 
called  the  lovers'  telegraph,  consisting  of  a  membrane  stretched 
over  the  end  of  a  tube,  and  having  a  thread  attached  to  the  centre, 
the  other  cud  of  which  was  attached  to  a  similar  membrane. 

The  fact  that  spoken  words  were  distinctly  transmitted  by  the 
longitudinal  vibrations  of  the  thread  from  one  membrane  to  the 
ol'ijr,  confirmed  the  idea  that  I  lia<l  formed  something  like  ayear 
previous  to  this  time ;  and  it  immediately  solved  in  my  mind  the 
problem  of  making  a  tran.smitter  that  would  cojjy  electrically  the 
physical  vibrations  of  the  air  ])ro(luced  by  articulate  sounds.  I 
determined  to  put  this  into  practical  shaj>e  and  file  it  in  the 
records  of  the  Patent  OOice.  I  realized  that  this  would  be  a 
miitter  of  the  highest  importance  in  a  .'Scientific  jjoint  of  view;  but 
I  had  no  adequate  conception  of  its  value  in  a  commercial  .sense. 

As  early  as  March,  1874,  Dr.  Samuel  S.  White,  of  Phila- 
delpliia,  had  purchased  an  interest  in  all  of  my  tclcjihonic  inven- 
tions that  I  had  made  or  miglit  thereafter  make;  and,  as  he  had 
already  advanced  consideraljle  money  in  aid  of  their  development, 
I  felt  it  iiuumbent  upon  me  to  givt;  as  much  of  my  time  as  pos- 
sible to  what  seemed  to  be  tlie  most  practical  and  useful  feature, 
and  the  one  promising  the  most  immediate  returns — that  of  mul- 
tiple telegraphy.  I  therefore  concluded  to  .secure  the  articulating 
feature,  and  take  it  uj)  and  develop  it  more  com])letely  at  another 
time. 

About  the  loth  of  January,  1876,  I  went  to  Washington, 
where  I  spent  some  time  in  a.ssisting  my  attorney  in  the  prepara- 
tion of  a  number  of  ca^eA  which  had  been  accumulating  for  several 
months.  This  required  several  w^eeks  of  time.  While  there 
I  put  my  speaking  telejihone  transmitter  into  the  form  of  draw- 
ings and  specifications,  and,  as  my  model  was  not  yet  ready,  I 
determined  to  file  the  specification  as  a  caveat  Following  out  the 
suggestion  made  by  the  diaphragm  and  string  of  the  lover.s' 
telegrai)h,  I  designed  a  transmitting  apparatus  ■which  copied 
the  motions  of  the  diaphragm  electrically,  through  the  longi- 
tudinal vibrations  of  a  light  rod  attached  to  the  centre  of  the 
dia])}iragm.     These  electrical  vibrations  or  undulations  were  the 


202 


THE   SPEAKING   TELEPHONE. 


result  of  the  variationn  in  the  resistance  of  the  circuit  made  by 
the  longitudinal  motions  of  the  rod,  moving  in  a  yielding  sub- 
stiince  offering  a  considerable  resistance  to  the  juussage  of  the 
electric  current.  The  following  is  a  v(!rl)atim  (iopy  of  the  speci- 
fication, filed  in  the  United  States  Patent  OlTice,  February  14, 
1876: 

gray's  specification,  filed  kebkuary  14,  1876. 

To  all  whom  it  may  concern :  Be  it  known  that  I,  Elisha 
Gray,  of  Chicago,  in  the  County  of  Cook,  and  State  of  Illinois, 
have  invented  a  new  art  of  transmitting  vocal  sounds  telegraphi- 
cally, of  which  the  following  is  a  sjjccilication  : 

It  is  the  object  of  my  invention  to  transmit  the  tones  of  the 
human  voice  through  a  telcgra[)hic  circuit,  and  reproduce  them 
at  the  receiving  end  of  the  line,  so  that  actual  conversations  can 
be  carried  on  by  persons  at  long  distances  apart 

I  have  invented  and  patented  methods  of  transmitting  nmsical 
impressions  or  sounds  telegraphically,  and  my  present  invention 
is  based  upon  a  modification  of  the  principle  of  said  invention, 
which  .is  set  forth  and  described  in  letters  patent  of  the  United 
Stjites,  granted  to  me  July  27th,  1875,  respectively  mimbered 
166,095  and  166,096,  and  also  in  an  application  for  letters 
patent  of  tlu^  United  States,  filc^d  by  me,  February  23,  1875. 

To  attain  the  objects  of  my  invention,  I  devised  an  instrument 
capable  of  vibrating  responsively  to  all  the  tones  of  tlie  liuraan 
voice,  and  by  which  they  are  render  3d  audible. 

In  the  accompanying  drawings  I  have  shown  an  apparatus 
embodying  my  improvements  in  the  best  way  now  known  to 
me,  but  I  contemplate  various  other  applicuitions,  and  also 
changes  in  the  details  of  construction  of  the  apparatus,  some  of 
which  would  obviously  suggest  themselves  to  a  skilful  electri- 
cian, or  a  j)erson  versed  in  the  science  of  acoustics,  on  seeing 
this  application. 

Fig.  1  represents  a  vertical  central  section  through  the  trans- 
mitting instrument; 

Fig.  2,  a  similar  section  through  the  receiver;  and 

Fig.  3,  a  diagram  representing  the  whole  apparatus. 


GRAY  S   SPECIFICATION. 


ao6 


't 


r 


>  ^ 


■liW" 


Mr/)/CSS£S. 


m/rMMTQiti 


Mg.  98. 


SLU€i^ 


204 


THE    SPEAKING    TELEPHONE. 


My  present  belief  is  that  the  most  effective  method  of  pro- 
viding an  apparatus  capable  of  responding  to  the  various  tones 
of  the  human  voice,  is  a  tympanum,  druni  or  diaphragm, 
stretched  across  one  end  of  the  chamber,  carrying  an  apparatus 
for  producing  fluctuations  in  the  potential  of  the  electric  current, 
and  consequently  varying  in  its  power. 

In  the  drawings,  the  pci-son  transmitting  sounds  is  shown  as 
talking  into  a  box,  or  chamber.  A,  acro.ss  the  outer  end  of  which 
is  stretched  a  diaphragm  a,  of  some  thin  substance,  such  as 
parchment  or  gold-beaters'  skin,  capable  of  responding  to  all  the 
vibrations  of  the  human  voice,  whether  simple  or  complex. 
Attached  to  this  diaphragm  is  a  light  metal  rod,  A',  or  other 
suitable  conductor  of  electricity,  which  extends  into  a  vessel  B, 
made  of  glass  or  other  insulating  material,  having  its  lower  end 
closed  by  a  plug,  which  may  be  of  metal,  or  through  which 
passes  a  conductor  b,  forming  part  of  the  circuit. 

This  vessel  is  filled  with  some  liquid  ])ossessing  high  resist- 
ance, such,  for  instance,  as  water,  so  that  the  vibrations  of  the 
plunger  or  rod  A',  which  does  not  quite  touch  the  conductor  b, 
will  cause  variations  in  resistance,  and,  consequently,  in  the 
potential  of  the  current  ])assing  through  the  rod  A'. 

Owing  to  this  construction,  the  resistance  varies  constantly  in 
response  to  the  vibrations  of  the  diaphragm,  which,  although 
irregular,  not  only  in  their  amplitude,  but  in  rapidity,  arc  never- 
theless ti'aiismitted,  and  can,  consequently,  be  transmitted  through 
a  single  rod,  which  could  not  be  done  with  a  positive  make  and 
break  of  the  circuit  employed,  or  where  contac;t  ])oints  are  used. 

I  contemplate,  howe\  or,  the  use  of  a  series  of  diai)hragms  in  a 
common  vocalizing  chamber,  each  diaphragm  carrying  an  inde- 
pendent roil,  and  responding  to  a  vibration  of  dilTerent  rapidity 
and  intensity,  in  which  case  contact  points  mounted  on  other 
diaphragms  may  be  employed. 

The  vii)rations  thus  imparted  are  transmitted  through  an  elec- 
tric circuit  to  the  receiving  station,  in  which  circuit  is  included 
an  electro-magnet  of  ordinary  construction,  acting  upon  a  dia- 
phragm to  which  is  attached  a  piece  of  soft  iron,  and  wliich 


BELLS   SPECIFICATION. 


205 


the 


diaphragm  is  stretched  across  a  receiving  vocalizing  chamber  c, 
somewhat  similar  to  the  corresponding  vocalizing  chamber  A. 

The  diaphragm  at  the  receiving  end  of  the  line  is  tlius  thrown 
into  vibrations  corresponding  with  those  at  the  transmitting  end, 
and  audible  sounds  or  words  are  })roduced. 

The  obvious  practical  application  of  my  improvement  will  be 
to  enable  persons  at  a  distance  to  converse  with  each  other 
through  a  telegraphic  circuit,  just  as  they  now  do  in  each  other's 
presence,  or  through  a  speaking  tube. 

I  claim  as  my  invention  the  art  of  transmitting  vocal  sounds 
or  conversations  telegraphically  through  an  electric  circuit. 

Although  it  is  not  my  intention,  as  I  said  in  the  beginning,  to 
raise  the  question  of  priority  of  invention  as  between  myself  and 
other  parties,  I  will  nevertheless  state  in  this  connection,  that  so  far 
as  I  ;im  aware,  this  is  tiie  lirst  description  on  record,  of  an  articu- 
liitiiig  telephone  wliich  transmits  the  spoken  words  of  the  human 
voice  telegraphically  liy  means  of  electricity. 

hell"s  specificatiox,  filed  FEimrAnv  14,  1876. 

In  order  that  the  claims  of  Professor  A.  G.  Bell  to  the  inven- 
tion of  the  speaking  tele[)hone  may  be  contrasted  with  those  of 
Mr.  KlishaGray,  we  reproduce  the  specifications  and  drawings  of 
the  former  as  they  were  filed  in  the  United  States  Patent  OfHce, 
on  the  14th  February,  187(5,  the  same  day,  it  will  be  observed, 
on  which  ^Ir.  Gray  filed  his  caveat. 

To  all  whom  it  itiay  concern  :  Be  it  known  that  I,  Alex- 
ander Graham  Bell,  of  Salem,  Massat-husetts,  have  invented 
certain  new  and  u.sefid  improvements  in  telegraphy,  of  which  the 
following  is  a  specification  : 

In  letters  jiatcnt  granted  to  mo  April  6,  1875,  No.  161,739,  I 
have  deseril)ed  a  method  of,  and  apparatus  for,  transmitting  two 
or  more  telegrapliic  signals  simultaneously  along  a  single  wire 
])y  the  employment  of  tran.smitting  instruments,  each  of  which 
occasions  a  succession  of  electri'^al  impulses  differing  in  rate  from 
the  others ;  and  of  receiving  instruments,  each  tuned  to  a  pitch 


206 


THE   SPEAKING  TELEPHONE. 


at  wliicli  it  will  be  put  in  vibration  to  produce  its  fundamental 
note  by  one  only  of  the  transmitting  instruments  ;  and  of  vibra- 
tory circuit-brcakei"s  operating  to  convert  the  vibratory  move- 
ment of  the  receiving  instrument  into  a  permanent  make  or  break 
(as  the  case  maybe)  of  a  local  circuit,  in  wliicli  is  placed  a  Morse 
sounder,  register,  or  other  tclegraj)hic  a2)paratus.  I  have  also 
therein  described  a  form  of  autograph  telegi'aph  based  upon  the 
action  of  the  above  mentioned  instruments. 

In  illustration  of  my  method  of  multiple  telegraphy  I  have 
shown  in  the  patent  aforesaid,  as  one  form  of  transmitting  instru- 
ment, an  electro-magnet  having  a  steel  s[)ring  armature,  which  is 
kept  in  vibration  Jjy  tl;e  action  of  a  local  battery.  This  arma- 
ture in  vibrating  makes  and  breaks  the  main  circuit,  jiroducing 
an  intermittent  current  upon  the  line  wire.  I  have  found,  how- 
ever, that  upon  this  plan  the  limit  to  the  number  of  signals  that 
can  be  sent  simultaneously  over  the  same  wire  is  very  speedily 
reached ;  for,  when  a  nundjcr  of  transmitting  instruments,  having 
different  rates  of  vibration,  are  simultaneously  making  and  break- 
ing the  same  circuit,  the  effect  ujion  the  main  line  is  practically 
equivalent  to  one  continuous  current 

In  a  pending  application  for  letters  patent,  filed  in  the  United 
States  Patent  Olhce  February  25, 1875, 1  have  described  two  ways 
of  producing  the  intermittent  current — the  one  by  actual  make  and 
break  of  contact,  the  other  by  alternately  increasing  and  diminish- 
ing the  intensity  of  the  current  without  actually  breaking  tlie 
circuit  The  current  produced  by  the  latter  method  I  shall  term, 
foi-  distinction  sake,  a  pulsatory  current 

My  present  invention  consists  ir  the  employment  of  a  vibra- 
tory or  undulatory  current  of  electricity,  in  contradistinction  to  a 
merely  intermittent  or  pulsatory  current,  and  of  a  method  of,  and 
apj^aratus  for,  producing  electrical  undulations  upon  thf"  Mne  wire. 

The  distinction  between  an  undulating  and  a  pu...aory  cur- 
rent will  be  understood  by  ccjusidering  that  electrical  pulsations 
are  caused  by  sudden  or  instantaneous  changes  of  intensity,  and 
that  electrical  undulations  result  from  gradual  clianges  of  in- 
tensity exactly  analagous  to  the  changes  in  the  density  of  air 


bell's  specification. 


207 


occasioned  by  simple  pendulous  vibrations.  The  electrical  move- 
ment, like  the  aerial  motion,  can  be  represented  by  a  sinusoidal 
curve  or  by  the  resultant  of  sovcrul  sinusoidal  curves. 

Intermittent  or  jnilsatory  and  undulatory  currents  may  be  of 
two  kinds,  accordingly  as  the  successive  impulses  have  all  the 
same  polarity  or  are  alternately  positive  and  negative. 

The  advantages  I  claim  to  derive  from  the  use  of  an  undulatory 
current  in  place  of  a  merely  intermittent  one  are,  first,  that  a 
very  much  larger  number  of  signals  can  be  transmitted  simul- 
taneously on  the  same  circuit ;  second,  that  a  closed  circuit  and 
.single  main  battery  may  be  used;  third,  that  communication  in 
both  directions  is  estaljlished  without  the  necessity  of  special 
induction  coils;  fourth,  that  cable disi)atches  maybe  transmitted 
more  rapidly  than  by  means  of  an  intermittent  current  or  by  the 
methods  at  present  in  use  ;  for,  as  it  is  unnecessary  to  discharge 
tile  cal)le  before  a  new  signal  car  be  made,  the  lagging  of  cable 
signals  is  jn'cvented  ;  fifth,  and  that  as  the  circuit  is  never  broken, 
a  spark-arrest(3r  becomes  unnecessary. 

It  has  long  been  known  that  when  a  permanent  magnet  is 
caused  to  approacli  the  ])ole  of  an  electro-magnet  a  current  of 
electricity  is  induced  in  the  coils  of  the  latter,  and  that  when  it 
is  made  to  recede  a  current  of  opposite  polarity  to  the  finst  appears 
upon  the  wire.  When,  therefore,  a  permanent  magnet  is  caused 
to  vibrate  in  front  of  the  ])ole  of  an  electro-magnet  an  undulatory 
current  of  electricity  is  induced  in  the  coils  of  the  electro-magnet, 
the  undulations  of  which  correspond,  in  rapidity  of  succession, 
to  the  vibrations  of  the  magnet,  in  ])olarity  to  the  direction  of 
its  motion,  and  in  intensity  to  the  amplitude  of  its  vibration. 

'Jliat  tlio  difference  between  an  undulatory  and  an  intermit- 
tent current  maybe  more  clearly  understood,  I  shall  describe  the 
condition  of  the  electrical  current  when  the  attcmj)t  is  made  to 
transmit  two  musieal  notes  .simultaneously — first  upon  the  one 
plan  and  then  upon  the  other.  Let  the  interval  between  the 
two  sounds  be  a  major  third ;  then  their  rates  of  viV)ration  are  in 
the  ratio  of  4  to  5.  Now,  when  the  intermittent  current  is  useil, 
the  circuit  is  made  and  broken  four  times  by  one  transmitting 


208 


THE   SPEAKIXCt  TELEPHONE. 


instrument  in  the  same  time  that  five  makes  and  breaks  are 
caused  by  the  otlier.  A  and  B,  figs.  1,  2  and  3,  represent  the 
intermittent  currents  ])rodueed-  four  impulses  of  B  being  made 
in  the  same  time  as  five  impulses  of  A.  c  c  c,  etc.,  show  where 
and  for  Ikjw  long  the  circuit  is  made,  and  d  d  d,  etc.,  indicate 
the  duration  of  the  breaks  of  the  circuit  The  line  A  and  B 
shows  the  total  effect  upon  the  current  when  the  transmitting 
instruments  for  A  and  B  are  caused  simultaneously  to  make 
and  break  tlie  same  circuit  The  resultant  effect  depends  very 
much  upon  the  duration  of  the  make  relatively  to  the  break.  In 
fig.  1  the  ratio  is  as  1  to  4 ;  in  lig.  2,  as  1  to  2  ;  and  in  fig.  3  the 
makes  and  breaks  are  of  equal  duration.  The  combined  effect, 
A  and  B,  fig.  3,  is  very  nearly  equivalent  to  a  contimious  cur- 
rent. 

When  many  transmitting  instruments  of  different  rates  of 
vibration  are  simultaneously  making  and  breaking  the  same 
circuit,  the  current  upon  the  main  lines  becomes  for  all  practical 
purjKises  continuous. 

Next,  consider  the  effect  when  an  undulatory  current  is  em- 
ployed. f]lectrical  undulations,  induced  by  the  vibration  of  a 
body  capable  of  inductive  action,  can  be  represented  graphically, 
without  error,  by  the  same  sinu.soidal  curve  which  expresses  the 
vibration  of  the  inducing  body  itself,  and  the  effect  of  its  vibra-'' 
tion  u})on  the  air;  for,  as  above  stated,  the  rate  of  oscillation  in 
the  electrical  current  corresponds  to  the  rate  of  vibration  of  the 
inducing  body — that  is,  to  the  pitch  of  the  .sound  produced. 
The  intensity  of  the  current  varies  with  the  amplitude  of  the 
vibration — that  is,  with  the  loudness  of  the  sound ;  and  the 
polarity  of  the  current  corresponds  to  the  direction  of  the  vibrat- 
ing body— that  is,  to  the  condensations  and  rarefactions  of  air 
produced  by  the  vibration.  Hence,  the  sinusoidal  curve  A  or 
B,  fig.  4,  represents,  graphically,  the  electrical  undulations 
induc(?d  in  a  circuit  by  the  vibration  of  a  body  capable  of 
inductive  action. 

The  horizontal  line  a  d  e/,  etc.,  represents  tlie  zero  of  current 
The  elevation  h  bh,  etc.,  indicates  impubsesof  positive  electricity. 


BELT.  S  SPECIFICATION. 


20& 


N6.174.465i 


A.  a.  BELL 


JSheels-SkeMl. 


Ttleatei  Ksiicli  7.  1676. 


A   £.  tt  £.  d    £<*£.«^«. 


r't'^.i 


JB  - 
X«B-«      -— 


A  _. 

B  _ 


J^'iif  Z. 


JB  _ 


y-ufS. 


y''^.«' 


"dx^xK^^i^^ 


AtB, 


A-f 


:Fof.s: 


irttHrsseti 


/Vj/.  99. 


^> 


TnvenTbr) 


^'/'^^^UJ^ 


210 


THE  SPEAKINCt  TELEPHONE. 


Sb.  174.465. 


A.  Q.  B£LL. 
TELSOSAFBT. 


Fig  6. 


Ptttntil  Mitcli  7.  1876. 


IFiff./ 


UritHcsms 


XnvenZOr* 


Fig.  100. 


UKI>L  S  .Sl'ECIFICATION. 


211 


Tiic  depressions  c  c  c,  etc.,  sliovv  impulses  of  nc^gativc  electrieity. 
The  vertieal  distance  b  d  or  cfoi  any  })ortion  of  tlio  eiirve  from 
the  zero  line  expresses  tlie  intcr.sity  of  the  positive  or  negative 
impulse  at  the  part  observed,  and  the  horizontal  distance  a  a 
indicates  the  duration  of  the  electrical  oscillation.  The  vibra- 
tions represented  by  the  sinusoi(hd  curves  B  and  A,  fig.  4,  are  in 
the  ratio  aforesaid,  of  4  to  5 — that  is,  four  OF('illations  of  B  are 
made  in  the  same  time;  as  five;  oscillations  of  A. 

Tiie  combined  elTectof  \  and  B,  when  induced  simultaneously 
on  the  same  circuit,  is  expressed  by  the  curve  A-j-B,  ^o-  "^t 
which  is  the  algebraical  sum  of  the  sinusoidal  curves  A  and  B. 
This  curve  A-|-B  also  indicates  the  actual  motion  of  the  air 
when  the  two  musical  notes  considered  are  .sounded  simul- 
t;meously.  Thus,  when  electrical  undulations  of  different  rates 
are  simultaneously  induced  in  the  .same  circuit,  an  eil'ect  is  pro- 
duced analogotis  to  that  occasioned  in  the  air  by  the  vibration 
of  the  inducing  bodies.  Hence,  the  coexistence  upon  a  tel(>- 
graphic  circuit  of  electrical  vibrations  of  ditVerent  pitch  is  mani- 
fested, not  by  the  obliteration  of  the  vibratory  character  of  the 
(•urrent,  but  by  iieculiarities  in  the  shapes  of  the  electrical  rnnlu- 
lations.  or,  in  otiier  wonls,  by  peculiarities  in  the  shapes  of  the 
<'urves  which  rcpre.si-nt  those  undulations. 

There  are  many  ways  of  producing  undulatory  currents  of 
electricity,  dependent  for  effect  upon  the  vibrations  or  motions 
of  liodies  caj)al)le  of  inductive  action.  A  f(>w  of  the  nujlhods 
that  may  be  employed  I  shall  hen;  specify.  When  a  wire, 
through  which  a  continiu)us  current  of  electricity  is  ])assing,  is 
caused  to  vibrate  in  the  neighborhood  of  anc^ther  wire,  an  undu- 
latory current  of  electricity  is  inducc^d  in  the  latter.  When  a 
<'ylinder,  upctn  which  are  arranged  bar  magnets,  is  made  to  rotate 
in  front  of  the  pole  of  an  electro-magnet,  an  undulatory  current 
of  ele(;tricity  is  induced  in  the  coils  of  the  electro-magnet. 

Undidations  are  caused  in  a  (continuous  voltaic  current  by  the 
vibration  or  motion  of  bodies  capable  of  inductive  action;  or 
by  the  vibration  of  the  conducting  wire  itself  in  the  neighbor- 
hood of  such  bodies.     Electrical  undulations  may  also  be  caused 


212 


TUE   Hl'KAKlNG  TKl.Kl'HONK. 


by  alternately  increasiii<^'  and  diminishing  tlie  resistance  of  tlio 
c'ircnit,  or  liy  alternately  incn-asingaiid  diniinisliing  the  jiower  of 
the  battery.  TIk;  internal  resistance  of  a  Lattery  is  diminished 
by  hrlnging  th(^  voltaic  elements  nearer  together,  and  increased 
by  placing  them  fartlu'r  apart.  The  reci])rocal  vibration  of  the 
elements  of  a  battery,  therefore,  occasions  an  undulatory  action 
in  the  voltaic  current.  The  external  resistance  may  also  bo 
varied.  For  instance,  let  mercury  or  some  other  liquid  form 
part  of  a  voltaic  circuit,  then  the  more  deejay  the  conducting 
wire  is  immersed  in  the  mercury  or  other  liquid,  the  less  resist- 
ance does  the  licpiid  offer  to  the  passage  of  the  current,  irenee, 
the  vibration  of  the  conducting  wire  in  mercury  or  other  liipud 
included  in  the  circuit  occasions  undulations  in  the  current.  The 
vertical  vibrations  of  the  elements  of  a  battery  in  the  liquid  in 
which  they  are  immersed  produces  an  undulatory  action  in  the 
current  by  alternately  iucreasing  and  diminishing  the  jwnver  of 
the  liattcry. 

In  illustration  of  the  method  of  creating  electrical  undulations, 
I  shall  show  and  describe  one  form  of  apparatus  for  producing 
the  effect.  I  prefer  to  em]iloy  for  this  ])urpose  an  electro-magnet 
A,  fig.  5,  having  a  coil  upon  only  one  of  its  legsi.  A  steel  sjjring 
armature  c  is  iirndy  clamped  by  one  extremity  to  the  uncovered 
leg  d  of  the  magnet,  and  its  free  end  is  allowed  to  project  above 
the  pole  of  the  covered  leg.  The  armature  c  can  be  set  in 
vibration  in  a  variety  of  ways,  one  of  which  is  by  wind,  and,  in 
vibrating,  it  ])roduces  a  musical  note  of  a  certain  delinite  pitch. 

When  the  instrument  A  is  placed  in  a  voltaic  circuit,  g  h  efg, 
the  armature  c  becomes  magnetic,  and  the  polarity  of  its  free  end 
is  op()osed  to  that  of  the  magnet  underneath.  So  long  as  the  ar- 
mature c  remains  at  rest  no  effect  is  produced  upon  the  voltaic 
current,  but  the  moment  it  is  set  in  vibration  to  produce  its  mu- 
sical note  a  powerful  inductive  action  takes  place,  and  electrical 
undulations  traverse  the  circuit  g  h  efg.  Tin;  vibratory  current 
])assing  through  the  coil  of  the  electro-magnet/causes  vibration 
in  its  armature  A,  when  the  armatures  c  h  of  the  two  instrumentii 
A  I  are  normally  in  unison  with  one  another ;  but  the  armature  /* 


IJKLL  S   SI-KCIKICATIOX. 


218 


is  unaflecttvl  Ijy  tlie  ])assag('  of  tlic  iuiiluliit<irv  purrcnt  when  the 
jiitchcs  (if  the  two  instniineiits  aredilTerent. 

AnunilxTof  iiistruiiieiits  may  bo  pLiccd  ujion  a  teU-grapliic 
circuit,  as  in  lig.  6.  When  tlio  armature  of  any  one  of  tlic  in- 
struments is  set  in  vibration,  all  the  other  instruments  upon  the 
cireuit  which  are  m  unison  with  it  resjwnd,  but  those  which, 
have  normally  a  diilcrent  rate  of  vibration  remain  silent.  Thus, 
if  A,  fig.  6,  is  set  in  vibration,  the  armatures  of  A^  and  A^  will 
vibrate  also,  but  all  the  others  on  the  circuit  will  remain  still.  So  if 
B^  is  caused  to  emit  its  musical  note,  the  instnuncnts  B  B-  re- 
spond. They  continue  sounding  so  long  as  the  mechanical  vibra- 
tion of  B^  is  continued,  lint  l)ccomo  silent  with  the  cessation  of 
its  motion.  The  duration  of  the  sound  may  be  used  to  indicate 
the  dot  or  dash  of  the  Morse  alj)habet,  and  thus  a  telegraphic 
dispatch  may  be  indicated  liy  alternately  interrupting  and  renew- 
ing the  sound.  "When  two  or  more  instruments  of  dilTerent 
pitch  are  simultaneously  caused  to  vibrate,  all  the  instruments  of 
corres])onding  jiitches  upon  the  circuit  arc  S(^t  in  vibration,  each 
responding  to  that  one  only  of  the  tran.'smitting  instruments 
with  which  it  is  in  uni.son.  Thus  the  signals  of  A,  fig.  6,  are  re- 
peated by  A^  and  A-,  liut  by  no  other  instruments  upon  the 
circuit;  the  signals  of  B^  by  B  and  B'  ;  and  the  signals  of  C^ 
T)y  C  and  C^ — -whether  A,  B-  and  C^  are  successively  or  simul- 
taneously caused  to  vibrate.  Hence  by  these  instruments  two 
or  more  telegraphic  signals  or  mcs.sagcs  may  be  sent  simulta- 
neously over  the  same  circuit  without  interfering  with  one 
another. 

I  desire  hero  to  remarlc  that  there  are  many  other  uses  to  which 
these  instruments  }nay  be  ])ut,  such  as  the  simultanco\is  trans- 
mission of  musical  notes,  differing  in  loudness  as  well  as  in  pitch, 
and  the  telegraphic  ti'ansmission  of  iioisesor  soinuls  of  any  kind. 

AVhen  the  armaturi;  c,  fig.  5,  is  set  in  vibration,  the  armature  h 
responds  not  only  in  pitch,  but  in  loudnc-^.s.  Thus,  when  c 
vibrates  with  little  amplitude,  a  very  soft  musical  note  proceeds 
from  /(  /  and  when  c  vibrates  forcibly  the  amplitude  of  the  vibra- 
tion of   h   is  considerablv  inercased,  and   the  resultinu'  sound 


214 


THE   SI'KAKINO   TKLKl'IIONK. 


becomes  louder.  So,  if  A  uikI  B,  fig.  6,  arc  sounded  simul- 
tiiiicoiisly  (A  loudly  and  15  .softly),  the  instruuicnt.s  vV  iiud  A* 
repeat  loudly  the  signal.s  of  A,  and  J}'  B-  repeat  softly  tho.so 
of  B.  '  .  ■ 

One  of  tin?  ways  in  wliieli  tlie  armature  c,  fig.  5,  may  bo  set  in 
vibralion  lias  been  state(l  before  to  be  by  wind.  Aiiollier  mode 
is  f^liown  in  fig.  7,  whereby  motion  can  be  imparted  to  the  arma- 
ture by  the  human  voice  or  by  means  of  ii  musical  instrument 

Tlui  armature  c,  fig.  7,  is  fastened  loosely  by  one  extremity  to 
the  uncovered  leg  d  of  the  electro-magnet  b,  and  its  other 
extremity  is  attached  to  the  centre  of  a  stretched  membrane,  a. 
A  cone,  A,  is  u.^ed  to  converge  sound-vibrations  upon  the  mem- 
brane. When  a  sound  is  uttered  in  the  cone  the  membrane  a  is 
.set  in  vil)ration,  the  armature  c  is  forced  to])artakco£  the  motion, 
and  thus  electrical  umbdations  are  created  u])()n  the  circuit 
E  h  efg.  These  undulaticuis  are  similar  in  form  to  the  air 
vibrations  caused  by  the  sound — that  is,  they  are  represented 
gi'aphically  by  similar  curves.  The  undulatory  current  passing 
through  the  electro-magnc^ty'  influences  its  armature  /*  to  co])y 
the  motion  of  the  armature  c.  A  similar  sound  to  that  uttered 
into  A  is  then  heard  to  proceed  from  I. 

In  this  .specification  the  three  words,  "oscillation,"  "vibra- 
tion," ami  "  undulation,"  .;ire  used  synonymously,  ami  in  con- 
tradistinction to  the  terms  "  iiitcnnitteut  "  and  "pul.satory."  By 
the  term  "body  capable  of  iiuliictivo  action,"  I  mean  a  body 
■which,  when  in  motion,  2)rodnces  dynamical  electricity.  I 
include  in  the  category  of  bodies  capable  of  inductive  action 
brass,  copper,  and  other  metals,  as  well  ;i-i  iron  and  .steel. 

Having  described  my  invention,  wdiat  I  claim,  and  d(;sire  to 
secure  by  letters  patent,  is  as  follows: 

1.  A  system  of  tel(\gra])hy  in  which  the  reiieiver  is  set  in 
vibration  by  the  (employment  of  undulatory  currents  of  ehx-tricity, 
substantially  as  set  forth. 

2.  The  combination,  substantially  as  set  forth,  of  a  permanent 
magnet  or  other  body  (!a[)able  of  inductive^  action,  with  a  (tlosed 
circuit,  so  that  the  vibration  of  the  one  .shall  occasion  electrical 


bell's  specification. 


ai6 


undulations  in  the  other,  or  in  itself,  and  this  I  claim,  whetiicrtlie 
permanent  magnet  bo  set  in  vibration  in  the  neighborhood  of  the 
eoiiducting  wire  fonning  the  circuit,  or  whether  the  conducting 
wire  1)0  set  in  vibration  in  the  neighborhood  of  the  iK^rmunent 
magnet,  or  whether  the  conducting  wire  and  the  ])errnanent  mag- 
net both  simultaneously  be  set  in  vibration  in  each  other's  neigh- 
borhood. 

3.  The  method  of  pvodncmg  undulations  in  a  continuous 
voltaic  current  by  the  vibration  or  motion  of  bodies  capable  of 
inductive  action,  or  by  the  vibration  or  motion  of  the  conducting 
wire  itself,  in  the  neighborhood  of  such  bodies,  as  set  forth. 

4.  Tiie  method  of  jirodueing  undulations  in  a  continuous 
voltaic  circuit  by  gradually  increasing  and  diminishing  the  re- 
sistance of  the  circuit,  or  by  gradually  increasing  and  diminishing 
the  power  of  the  battery,  as  set  forth. 


5.  The  method  of,  and  apparatus  for,  transmitting  vocal  or 
other  sounds  ttilegraphieally,  as  herein  described,  by  causing 
electrical  undulations,  similar  in  form  to  the  vibrations  of  the 
air  accompanying  tlie  said  vocal  or  other  sounds,  substantially  fia 
set  forth. 

We  have  given  in  Chapter  11.  a  verbatim  copy  of  a  lecture 
delivered  by  Professor  Bell,  before  the  Society  of  Telegraphic 
Engineers,  in  London,  October  31,  1877.  On  page  71  the  pre- 
ceding cut,  lig.  101,  is  shown,  which  is  the  only  instrument 
in  the  i.atent  of  March  7,  1876  (filed  February  14,  187(>)  for 
which  any  pretenc(!  can  be  set  uj)  that  it  is  a  talking  telephone. 
Speaking  of  this  instrument,  Pi-ofessor  Bell  says,  that  Mr.  Wat- 


21  fi 


TllK   SJ'KAKIN(i-  'I'Kl-KI'IloNK. 


Fvj.  102. 


ORAY  S   CAVEAT. 


217 


son,  wliilc  tryiii,^  it  witli  liim,  declared  tliut  "lie  Iniinl  :i  faint 
souikI"  from  it,  l)iit  Professor  Bell  could  not  vcrifv  his  iissertioii. 
Xow,  the  "  fniiit  sound  "'  heard  liy  ^^r.  Watsoii  cannot  Ik;  claimed 
to  lie  articul.,;e  speech,  and  tiie  |ierson  who  lirst  olitained  arlicu- 
lat(i  uttei'ance  from  the  lelephono  is  the  discoverer.     Mr.  Oniy's 


a\i'at   of   the  same  date  si 


lows  niciins  ot  pi'oduenii'  av 


rticulate 


s|iccch  teli'|ihonically  (li;.''.  I(i2).  and  states  that  "it  will  (muhle 
|iiison.s  at  a  distance  to  converse  with  each  otliM-  ihroujfh  a  telc- 
jrrapliie  I'ircnit,  just  us  they  now  do  in  each  other's  ])reaence,  or 


throu^ii  a  sjieakinLC 


tul. 


IJeferrinjf  to  Prof.  Rell's  descri[ition,  on  ]k\isg  71,  of  the  instru- 
ment with  which  lie  iirst  ol)tained  audil)le  eU'ects  (lijf.  ijO),  it 
will  lie  seen  that  it  is  precisely  the  same  in  jirinciple,  and  almost 
identical  in  construction,  with  the  receiving  instrument  ."^h 


own 


ind  (tescri 


bed  in  ^fr.  Gray's  cav(>at  of  Fehruary  14,  ISTH.     Prof. 


Pell,  it  is  claiii 


ilitaineil  his  lirst  audil>le  soiimls  of  articulate 


spei'ch  in  the  spring'  of  1870.  Here,  then,  are  two  important 
facts  bcaiMiig  on  the  ([U("stioii  of  priority  in  the  invention  of  the 
speaking  tele])lione.  Mr.  (iray  dcscrihcil  ami  illustrated  his 
.speaking  telephone  in  the  winter  of  ls70.  In  the  following 
spi'ing  Prof.  Bell  obtained  his  iirst  audilile  eiVeets  in  the  repro- 
ducti(jn  of  articulate  speech  at  a  distance  by  electro-magnetism, 
asnd  crn])loyed  for  this  ])ur])o.«e  an  apparatu.s  similar  to  that 
w 


m 


lich  was  illustrated  and  described  in  ^fr.  (Jray's  cav(>at,  tiled 
the  I'nited  States  Patent  OfTico  the  jireceding  Febniary. 
Whether  or  not  Prof.  Bell  inv(>nted  the  ap]>aratus  independently 
of  Mr.  Grav,  we  have  no  means  of  juilgine';  but  that  ho  was  not 


the  iirst  inventor,  we  thiidc  the  facts  conclnsivelv  si 


low. 


Ihi 


Le  been  the  iirst  to  inv(Mit  it,  is  thei'c  anv  i 


'casou  w 


hv  1 


iC  SllOUl( 


no 


t  hav(!  described  it  in 


IIS 


4'1 


ilication 


filed: 


iniUitaueousJv  with 


Mr.  (Irav,  on  tlus  1-ith  of  Pobruarv,  1«76: 


CIIAPTER  VI. 


EDISOXS    TEI.KI'HOXIC    KKSEAUCIIES. 


The  followiii''  fominmiicutiou  from  Mr.  Thomas  A.  Edison 
gives  a  detailotl  account  ot"  his  researches  in  telephony,  and  is  a 
valuable  contribntion  to  the  history  of  the  dovelopnieut  of  the 
speaking  tclei)hone. 

Some  time  in  or  about  the  niontli  of  July,  1875,  I  began 
experimenting  with  a  system  of  mvdtiple  telegraphy,  which  had 
for  its  basis  the  transnussion  of  acoustic  vibrations.  Being  fur- 
nished, at  the  same  time,  by  Hon.  William  Orton,  President  of 
the  AVestern  Union  T(>lcgraph  Company,  with  a  translated 
description  from  a  foreign  seientitic  journal  of  lieisss^  tel<>phone, 
I  also  began  a  series  of  experiments,  with  the  view  of  producing 
an  articulating  telephone,  carrying  on  both  series  simultaneously, 
by  the  aid  of  my  two  assistants,  Messrs.  Batchclor  and  Adams. 

With  regard  to  the  multiple  telegrajjli  1  will  say  that  many 
methods  were  devised,  among  which  may  be  mentioned  the 
transfer  system.  This  consi.sted  in  cond)ining  a  largo  tuning 
fork  with  multiple  foi'ks,  so  arranged  at  two  terminal  stations, 
with  contact  springs  leading  to  diil'erent  Morse  instruments,  that 
the  synchronous  vibrations  of  the  forks  would  change  the  main 
line  wires  from  one  .set  of  instruments  to  other  sets  at  both  sta- 
tions, at  a  r.ate  of  120  times  ])er  .sectrnd.  AVith  this  rate  of  vii)ra- 
tion  the  wire  would  be  simultaneously  disc(jimected  at  both  ter- 
minal stations  from  ouo  set  of  ^[orse  signalling  a|)[)ai'atus,  .'ind 
momentarily  placeil  in  alternate  comiection  Avitii  three  other 
similar  sets  of  a])paratus,  and  tiicn  again  returned  to  tiie  lirst  set, 
witliout  I  ..using  the  ap[)aratus  to  mark  theabsenceof  the  current 
otherwise  than  by  a  percc[itil>h;  weakening  of  the  same. 


1  Zeit«olirift  ties  DiMltscli-Oestorreicliidolii'li  TeU'tfruplu-n-Viircins,  lu'raiisf^'ctrebeii 
in  (lessen  Aiiltrat;!'  von  dvr  Kr.ni^'licli  I'nnissisclicn  TL'lc!,'raplicM-I)in  rliuTi.  l{cili- 
trirt  vim  Dr.  J'.  Willicliii  Hrix.  Vol.  ix.,  Iwi'j,  puj^u  jL'fi.  (For  ii  descrijitiyii  ol'  Uuisu's 
;4  |)iiratUH  HCM'  [.iijios  '.>  t')  l-'t,  ilR'lilrtivu.) 


TELEI'HOXIO   RECEIVERS. 


219 


By  tliis  means,  therefore,  four  perfectly  independent  wires 
were  praetically  created,  npon  which  signalling  could  be  carried 
on  with  any  system  which  was  worked  no  faster  than  the  ordi- 
nary ^lorse  system.  Each  of  these  wires  was  also  duplexed  and 
found  to  wcn-kpert'ectly  upon  a  line  of  artificial  resistancie,  thus 
allowing,  with  the  ordinary  apparatus,  of  the  simultaneous  trans- 
mission of  eight  different  messages. 

Notwithstanding  the  })erfect  success  of  the  system  upon  an 
artificial  line,  however,  which  posses.sed  little  or  no  electrostatic 
capacitv,  I  have  never,  in  practice,  heen  ahle  to  prodvu'e  a  sufli- 
ciently  perfect  compensation  for  the  effects  of  the  static  charge 


UNE 


Fitj.  lo;!. 

to  allow  (if  llic  successful  use  of  the  system  on  a  line  of  ovci' 
forty  miles  in  length,  although  1  have  i)ut  the  line  to  earth  at 
both  stations  after  it  leaves  one  set  of  instruments  and  before  it 
is  })laced  in  contact  with  another  set;  have  .sent  reversed  currents 
inlci  it,  and  have  also  used  magnelic  and  condenser  compensation 
ill  Narious  wavs,  knov.'u  to  experts  in  static  compensation,  but 
all  without  avail.  I\v  vibrating  tlu!  line  win^  betweiMi  two  .sets 
of  apparatus,  liowcxer,  good  satisfaction  has  been  ol)tained  on 
lines  of  about  200  niih  s  in  length. 

In  my  system  of  acoustic  transmission,  wliich  was  devi.sed  in 
September,  1875,  and  is  shown  in  tig.  10.'?,  two  tuning  fcirks,  A 


220 


TIIK   SPEAKING   TET.EPIIOXE. 


and  B,  vibrating  from  100  to  500  times  per  second,  were  kept  in 
continuous  motion  ])y  a  loctil  magnet  and  battery,  and  tlic  sliort 
circuiting  was  controlled  l)y  the  signalling  keys  Kj  and  Kg- 

As  will  bo  seen  on  reference  to  the  figure,  this  system,  like 
that  shown  in  my  patent  of  1873,  is  dependent  ujjon  tlic  vary- 
ing resistance  occasioned  hy  employing  a  movable  electrode  in 
water,  and  which  thus  produces  corres])onding  variations  of  the 
battery  current  in  the  lino. 

The  re(!eiver3  11^  and  Eg,  fig.  104,  were  formed  of  telescopic 
tubes  of  metal,  by  lengthening  or  shortening  of  which  the  column 
of  air  in  cither  could  be  adjusted  to  vibrate  in  unison  with  the 

LINE 


Fi'j.  nil. 

proj'cr  tmic  of  the  fork,  whose  signals  were  to  ]h\  I'cceived  bv 
each  particuhir  instrument.  An  inoi  diaplu'agm  M'as  soldered 
to  one  end  of  these  tul)cs.  and  the  latter  ])!ai'eil  in  sui'h  a  manner 
as  to  bring  the  dia[)hragm  of  each  resju'ctively  just  in  front  oi'an 
ekv  tro-magnet,  which,  in  action,  would  cause  them  to  viiinite. 
When  the  column  of  aii'  in  cither  receiver  was  jiroper'y  adju.st(>d 
to  a  gi\(m  tone,  the  signals  due  to  sto]i])iiig  and  starting  the 
vibrations  by  the  distant  key  were  very  jond,  as  compared  to 
other  tones  not  in  harmony  with  the  column  of  air.  FN  \ililc 
rubber  tubes,  with  car  pieces,  wci'(^  connected  to  thi'  I'cceiviM's,  so 


MAGNETO-SPEAKING   TELEPHONE. 


221 


that,  in  usiiif^f  the  instruments,  llie  liead  of  the  operator  was  not 
re([uired  to  be  held  in  an  unnatural  or  strained  position. 

This  system  worked  very  well ;  but  one  defeet  in  it  was 
apparent  fi'oin  the  lii>;t,  and  that  was  its  continual  teiulcney  to 
give  the  operator  what  is  termed  the  baek-sti'oke,  even  from  the 
slightest  cause,  such  as  the  opening  of  a  door  or  the  moving  of 
the  head,  and  also  occuiTed  on  the  slightest  inattention  whatever. 

With  a  Morse  sounder,  as  is  well  known,  every  dot  is  made 
apparent  to  the  ear  by  two  sounds,  the  first  being  produced  when 
the  lever  strikes  the  anvil,  and  the  other  wlieu  it  strikes  the; 
nppcr  or  back  contact.  A  dash,  like  the  dot,  is  als(j  composed 
of  two  sounds,  l)ut  the  interval  of  time  between  the  pi'oiluction 
of  tlie  first,  the  downward  stroke  orsouud  and  the  U])ward  stroke, 
is  what  determines  its  character.  Jt  fi'cMpiently  happens,  Jiow- 
evcr,  when  a  sounder  is  so  adjusted  that  the  .sound  produced  by 
the  down  stroke  is  of  the  same  volume  or  loudness  as  the  one 
given  by  the  up  stroke,  that  the  order  of  reading  becomes  re- 
versed on  the  slightest  disturbance  or  iiuittcntion  and  the  ear 
nustakes  the  up  .sound  for  the  dov/n  .sound,  and  vice  versa.  The 
signals  conseipiently  become  unintelligil)le,  and  the  operator  can 
only  restore  the;  proper  ()r(h>r  ])y  closing  botii  cars  and  watching 
■he  motion  of  the  sounder  lever,  or  by  deadening  the  back  sound 
iv  ]»laeing  the  finger  on  the  lever  until  the  ear  again  catches  a 
^'    rd  or  two. 

Similarly  with  the  musical  signals,  the  dots  and  dashes  are 
I'oiined  by  the  relative  short  or  long  duration  of  a  continuous 
tone,  l)ut  in  this  ca.se  the  pitch  is  always  the  same,  and  this  con- 
.stitutcs  an  element  of  confusion  that  is  qnit(!  as  bad  as  tlu^  back 
stroke  of  the  sounder  above  rcfeiTcd  to.  J  therefore  arranged 
my  keys  so  as  to  tiunsmit  two  short  tones  close  together  to  form 
a  dct,  and  two  tones  separateil  by  an  interval  to  form  a  dash  :  but 
there  was  still  so  little  distinctive  difi'ercnce  between  one  and  the 
other  that  J  was  led  to  defer  further  expcrinu-nt  with  the  appa- 
ratus for  a  time.  It  is  probable  that  soiuc!  means  will  be  fouiid 
for  ])rodu(  ing  a  greater  degree  of  difrert'nce  between  the  two  ele- 
ments of  the  signals,  such,  for  instance,  as  the  employment  of  two 


222 


THE   SPEAKING   TELEPHOXE. 


forks  of  slightly  different  ])itfli,  which,  at  least,  i)romises  well. 
When  this  is  done  the  system  will  be  of  some  value. 

It  will  he  noticed  that  tlie  receiving  instrument  shown  in  fig. 
104  CDutnins  the  diaphragm  magnet  and  chaml)er  of  the  magneto- 
speaking  '•  'r  le;  and  I  may  say  liere  that  Iljclievel  was  the 
first  to  devi.  u'atus  of  this  kind,  which  I  intended  for  use  in 

connection  win  eoustic telegrajths.  I  tan, however,  laynoclaim 
to  having;  discovered  that  convci'sation  could  he  cairied  on  Ix;- 
tween  one  receiver  and  the  other  upon  the  magneto  principle  by 
causing  the  voice  to  vibrate  the  (liai)hragm. 

Another  system  of  niuitiple  transmission  consisted,  partly,  in 
the  use  of  reeds  for  receivers,  and  has  been  exceedingly  well  de- 
veloped in  the  hands  of  Mi\  Klislia  tii'ay,  but  I  f()rbear  explain- 
ing it  here,  owing  to  its  complexity  and  lack  of  practical  merit 

My  first  attempt  at  constructing  an  articulating  telephone  was 
made  with  the  Reiss  transmitter  and  one  of  my  i-csonant  receivers 
described  above,  and  my  experiments  in  tliis  direction,  wliich 
continued  until  the  production  of  my  j)rescnt  carbon  telcj)honc, 
cover  many  thousand  pages  of  manuserij)t,  I  .shall,  however, 
describe  here  only  a  few  of  the  more  imporkmt  onc-^. 

In  one  of  the  llrst  experiments  I  included  a  simplified  Reiss 
transmitter,  having  a  platinum  .screw  facing  the  diaphragm,  in  a 
circuit  containing  twenty  cells  of  battery  and  the  resonant  re- 
ceiver, and  then  placed  a  drop  of  wat(>r  between  the  points;  the 
results,  however,  when  the  apparatus  was  in  action,  were  unsatis- 
factory— rapid  decomposition  of  the  water  took  iilace  and  a  de- 
posit of  sediment  was  left  on  the  platinum.  I  afterwards  u.sed 
disks  attached  both  to  the  diaphragm  and  to  the  .scnnv,  with  sev- 
eral drops  of  water  [jlaced  between  ami  held  there  by  capillary 
attraction,  but  rapid  decomposition  of  the  water,  which  was  im- 
pure, continued,  and  the  words  came  out  at  the  receiver  very 
much  confused.  Various  acidulated  .solutions  were  then  tried, 
but  the  confused  .sounds  and  decompositions  were  the  only 
results  obtained. 

With  distilled  water  I  could  get  nothing,  ])robably  because,  at 
that  time,  1  usc(l  very  thi(;k  iron   diaphragms,  as  1  have  since 


■ 


THE   CAKBON   TELEPirONE. 


223 


frequently  obtained  good  results ;  or,  jjossibl y,  it  was  because  the 
ear  was  not  yet  educated  for  this  duty,  and  therefore  I  did  not 
know  wliat  to  look  for.  If  this  was  the  case,  it  furnishes  a  good 
illustration  of  the  fact  observed  by  Professor  Mayer,  that  we 
often  fail  to  distinguish  weak  sounds  in  certain  cases  when  we 
do  not  know  what  to  expect 

Sj)onge,  i)a})er  and  felting,  saturated  with  various  solutions, 
were  also  used  between  the  disks,  and  knife  edges  were  substi- 
tuted for  the  latter  with  no  better  results.  Points  immersed  in 
electrolj'tic  cells  were  also  tried,  and  the  experiments  with  vari- 
ous solutions,  devices,  etc.,  continued  until  February,  1876,  when 
I  abandoned  the  decomposable  fluids  and  endeavored  to  vary  the 
resistance  of  the  circuit  j)roportionately  with  the  amplitude  of 
vibration  of  the  diaphragm  by  the  use  of  a  multiplicity  of  plat- 
inum points,  springs  and  resistance  coils— all  of  which  were  de- 
signed to  be  controlled  by  the  movements  of  the  diaphragm,  but 
none  of  the  devices  were  successful. 

In  the  spring  of  1876,  and  during  the  ensuing  summer,  I  en- 
deavored to  utilize  the  great  resistance  of  thin  films  of  plumbago 
and  white  Arkansas  oil  stone,  on  ground  glass,  and  it  was  here 
that  I  first  succeeded  in  conveying  over  wires  many  articulated 
seiit^'nccs.  S})rings  attached  to  'he  dia[)hragm  and  numerous 
other  devices  were  made  to  cut  in  and  out  of  circuit  more  or  less 
of  the  plumbago  lilm,  but  the  disturbances  which  the  devices 
themselves  caused  in  the  true  vibrations  of  the  diaphragm  pre- 
vented the  realization  of  any  practical  results.  One  of  my  as- 
sistants, however,  continued  tiic  experiments  without  intcrru]>- 
tion  until  January,  1877,  when  I  a})plied  the  peculiar  property 
which  semi-conductors  have  of  varying  their  resistance  with 
])ressur(',  a  fact  discoverecl  by  myself  in  1873,  while  constructing 
.some  rheostats  for  artificial  cables,  in  which  were  emj)loyed 
powdered  carbon,  plumbago  and  other  materials,  in  glass  tubes. 

For  the  })urpos(^  of  making  this  ai)[)lication,  L  constructed  an 
apparatus  ju-ovided  with  a  diaphragm  carrying  at  its  centre  a 
yielding  spring,  which  was  faced  with  platinum,  and  in  front  of 
this  I  placed,  in  a  I'up  seeui'cd  to  an  adjusting  screw,  sticks  of 


224 


THE  SPEAKING  TELEPHONE. 


crude  plumbago,  coiubiiied  in  various  proportions  witli  dry  Jiow- 
ders,  resins,  etc.  By  this  meaiis  I  succeeded  in  producing  a 
telephone  which  gave  great  volume  of  sound,  but  its  ai-ticuhition 
was  rather  poor;  when  once  familiar  witli  its  peculiar  sound, 
however,  one  ex^ierieuced  but  little  difliculty  iu  understanding 
ordinary  conversation. 

After  conducting  a  long  series  of  experiments  with  solid  ma- 
terials, I  finally  abandoned  them  all  and  sul)stitutcd  therefor 
tufts  of  conducting  fibre,  consisting  of  lloss  silk  coated  with 
plumbago  and  other  semi-conductons.  The  results  wei'e  then 
very  much  better,  but  wliile  the  volume  of  sound  was  still  great, 
the  articulation  was  not  so  clear  as  that  of  the  magneto  tele- 
phone of  Prof.  Bell.  'J'he  instrument,  besides,  rcipiired  very 
frequent  adjustment,  which  constituted  au  objectionable  feature. 

Upon  investigation,  the  difference  of  resistance  produced  by 
the  varying  pressure  upon  the  semi-conductor  was  found  to  be 
exceedingly  small,  and  it  occurred  to  me  that  as  so  small  a 
change  in  a  circuit  of  large  resistance  was  only  a  small  factor,  in 
the  primary  circuit  of  an  inducti(jn  coil,  where  a  slight  change  of 
resistance  would  be  an  impf)rtant  factor,  it  would  thus  enable  me 
to  obtain  decidedly  better,  results  at  once.  Tlie  experiment, 
however,  failed,  owing  to  the  great  resistance  of  the  semi-con- 
ductors then  used. 

After  further  experimenting  in  various  directions,  I  was  led 
to  believe,  if  I  could  by  any  means  reduce  the  ncjrmal  resistance 
of  the  semi-conductor  to  a  few  ohms,  and  still  effect  a  difference 
in  its  resistance  l)y  the  pressure  due  to  the  vibrating  diai)hragm, 
that  I  could  use  it  in  the  primary  circuit  of  an  induction  coil. 
Having  arrived  at  this  conclusion,  I  constructed  a  transmitter 
in  which  a  button  of  some  semi-conducting  substance  was  placed 
between  two  platinum  disks,  in  a  kind  of  cup  or  small  containing 
vessel.  Electrical  connection  between  the  button  and  disks  was 
maintained  by  the  slight  pressiire  of  a  piece  of  rubbei-  tubing,  J 
inch  in  diameter  and  ^  inch  long,  which  was  secured  to  the  dia- 
phragm, and  also  made  to  rest  against  the  outside  disk.  The 
vibrations  of   the  diaphragm   were  thus  able  to  produce  the 


THE   CARBON  TKLEPHONE. 


225 


requisite  pressure  on  the  platinum  disk,  iind  thereby  vary  the 
resistance  of  tlie  button  included  in  the  primary  circuit  of  the 
induction  coil. 

At  fii-st  a  button  of  solid  plumbago,  such  as  is  emplo\-ed  by 
electrotypers,  was  used,  and  the  results  obtained  \v(>r(;  considered 
excellent,  everything  transmitted  coming  out  moderately  dis- 
tinct, but  the  volume  of  s(jun(l  was  no  greater  than  that  of  the 
magneto  telephone. 

In  order,  therefore,  to  obtain  disks  or  buttons,  which,  with  a 
low  normal  resistance,  could  also  be  made,  by  a  slight  pressure, 
to  vary  greatly  in  this  respect,  1  at  once  tried  a  great  vai'iety  of 
substances,  such  as  conducting  oxides,  siUjihides  and  other  par- 
tial c<mductors,  among  whicli  was  a  small  rjuantit^,'  of  lamp- 
black that  had  been  taken  from  a  smoking  petroleum  lamp  and 
preserved  as  a  curiosity  on  account  of  its  intense  bhick  ct)lor. 

A  small  disk  made  of  this  substance,  wlien  ])laced  in  the  tele- 
phone, gave  splendid  results,  tlie  articulation  being  distinct,  and 
the  volume  of  sound  several  times  greater  than  with  telephones 
worked  on  the  magneto  jtrinciple.  it  was  soon  found  upon 
iii\'(>stigation,  that  the  resistance  of  the  disk  could  be  varied 
from  three  hundred  ohms  to  the  fractional  part  of  a  single  ohm 
by  jiressure  alone,  and  that  the  best  results  were  obtained  when 
the  resistance  of  the  itrimary  coil,  in  which  the  carbon  disk  was 
included,  was  -j-\  of  an  ohm,  and  the  normal  resistance  of  the 
disk  itself  three  ohms. 

Air.  Henry  Bentlev,  ]ir(>sident  of  the  Local  Telegraj)h  Com- 
jiany,  at  Philadelphia,  who  has  made  an  exhaustive  series  of 
experiments  with  a  complete  set  of  this  apparatus  upon  the 
wires  of  the  Western  Union  Telegraph  Company,  has  actually 
succeeded  in  working  with  it  over  a  wire  of  720  miles  in  length, 
and  has  found  it  a  practicable  instrument  upon  wires  of  100  to 
2()0  miles  in  length,  notwithstanding  the  fact  that  the  latter  were 
]>laced  upon  poles  with  numerous  other  wires,  wliich  occasioned 
sufTiciently  powerful  induced  currents  in  them  to  entirely  destroy 
the  articulation  of  the  nuigneto  telephone.  1  also  learn  that  he 
has  found  the  instrument  practicable,  when  included  in  a  Morse 


226 


THE   SPEAKING   TELEPHONE. 


circuit,  witli  a  battery  and  eiglit  or  ten  stations  provided  witli 
the  ordinaiy  Morse  apparatus ;  and  that  several  way  stations 
could  exchange  business  tclcphonically  upon  a  wire  ■\vhicli  was 
being  worked  cpiadruplex  without  disturbing  the  latter,  and  not- 
withstanding, also,  the  action  of  the  powerful  reversed  currents 
of  the  quadru})lex  on  the  diaphragms  of  the  receiver.  It  would 
thus  seem  as  thougli  the  volume  of  sound  produced  by  the  voice 
with  this  apparatus  more  than  compensates  for  the  noise  caused 
by  such  actions. 

While  engaged  in  experimenting  with  my  telephone  for  the  pur- 
pose of  ascertaining  whether  it  might  not  be  ])ossible  to  dispense 
with  the  rubbc'  tube  which  connected  the  diaphragm  with  the 
rheostatic  disk,  and  was  objectionable  on  account  of  its  tendency 
to  become  flattened  by  continued  vibrations,  and  thus  necessitate 
the  readjustment  of  the  instrument,  I  discovered  that  my  prin- 
cijile,  unlike  all  other  acoustical  devices  for  the  transmission  of 
speech,  did  not  require  any  vibration  of  the  diaphragm — that,  in 
fact,  the  sound  waves  could  be  transformed  into  electrical  pul- 
sations without  the  movement  of  any  intervening  mechanism. 

The  manner  in  which  I  arrived  at  this  result  was  as  follows: 
I  first  substituted  a  spiral  spring  of  about  a  quarter  inch  in 
length,  contiiining  four  turns  of  wire,  for  the  rubber  tube  which 
connected  the  diaphragm  with  the  disks.  I  found,  however,  that 
this  spring  gave  out  a  musical  tcme  which  interfered  somewhat 
with  the  clfects  produced  by  the  voice ;  but,  in  the  hope  of  over- 
coming the  defect,  I  kept  on  substituting  spiral  springs  of  thicker 
wire,  and  as  I  did  so  I  found  that  the  articulation  became  both 
clearer  and  louder.  At  last  I  sul)stituted  a  solid  substance  for 
the  springs  that  had  gradually  been  made  more  and  more  inelastic, 
and  then  I  obtained  very  marked  improvements  in  the  results. 
It  then  occurred  to  me  that  the  whole  question  was  one  of  pres- 
sure only,  and  that  it  was  not  necessary  that  the  diaphnigm  should 
vibrate  at  all.  I  consequently  put  in  a  heavy  diaphragm,  one 
and  three  quarter  inches  in  diameter  and  one  sixteenth  inch 
thick,  and  fastened  the  carbon  disk  and  plate  tightly  together, 
so  that  the  latter  showed  no  vil)ration  with  the  loudest  tones. 


THE   CARBON   TELEPHONE. 


227 


Upon  testing  it  I  found  iny  snrrnirtes  veviiied ;  tlic  articulation 
•was  perfect  and  the  volume  of  sound  so  great  that  conversation 
carried  on  in  a  whisper  three  feet  fi-oin  the  telephone  was  clearly 
heard  and  understood  at  tlie  otlier  end  of  the  line. 

Tiiis,  therefore,  is  the  arrangement  I  liuve  adopted  in  my  pres- 
ent form  of  a]-)parat)is,  which  I  call  the  carbon  telephone,  to  dis- 
tinguish it  from  others.  It  is  fully  described  in  another  part  of 
this  work. 

The  accessories  and  connections  of  this  apparatus  for  long  cir- 
cuits are  shown  in  lig.  105.    A  is  an  induction  coil,  whose  jiriraary 


Fig.  105. 

wire  p,  having  a  resistance  of  several  ohms,  is  ])laccd  ai'ound 
the  secondary,  instead  of  within  it,  as  in  the  usual  manner  of  con- 
struction. The  secondary  coil  s,  of  finer  wire,  has  a  resistance 
of  from  150  to  200  ohms,  according  to  the  degree  of  tension  re- 
quired ;  and  the  receiving  telephone  R  consists  simply  of  a  mag- 
net, coil  and  diaphragm.  One  pole  of  the  magnet  is  coimceted 
to  the  outer  edge  of  the  dinphragm,  and  the  other,  wliich  carries 
the  wire  bobbin  of  about  75  ohms  resistance,  and  is  included  in 
the  main  line,  is  placed  just  opposite  its  centre. 


228 


THE   SPEAKING   'J'KLEl'JIOXE. 


P  E  is  the  signalling  relay,  generally  a  SicMnens'  polarized  in- 
strument, which  has  been  given  a  bias  towards  one  side,  and  (!on- 
sequently  is  capable  of  rcsi)oiiding  to  currents  of  one  delinite 
direction  onl}^ 

The  lever  of  this  relay,  when  actuated  by  the  current  from  a 
distiuit  station  on  the  line  in  which  tlie  instrument  is  included, 
closes  a  local  circuit  containing  tlie  vibrating  call  bell  B,  and 
thus  gives  warning  when  S2)eaking  communication  is  desired. 

Besides  serving  to  opei-ate  the  call  bell,  tlie  local  l)attery  E  is 
also  used  for  sending  the  call  signal.  S  is  a  switch,  the  lever  of 
which,  when  placed  at  o,  between  miind  «,  disconnects  the  trans- 
mitter T  and  local  buttery  E  from  the  coil  A,  and  in  this  posi- 
tion leaves  the  polarized  relay  P  E  free  to  respond  to  cur- 
rents from  the  distant  station.  When  this  station  is  wanted, 
however,  the  lever  S  is  turned  to  the  left  on  ?i,  and  depressed  sev- 
eral times  in  rapid  succession.  Tlie  current  from  the  local  bat- 
tery, by  this  means,  is  made  to  jiass  through  the  primary  coil 
of  A,  and  tluis  for  each  make  and  break  of  tlic  circuit  induces 
powerful  currents  in  the  secondary  s,  which  pass  into  the  line 
and  actuate  the  distant  call  bell. 

When  the  call  signals  have  been  exchanged,  botli  terminal 
stations  place  their  switches  to  the  right  on  m,  and  thus  intro- 
duce the  carbon  transmitter  into  their  respective  circuits.  The 
changes  of  pressure,  produced  by  sjieaking  against  the  diaphragm 
of  either  transmitter,  then  serve,  as  already  shown,  to  vary  the 
resistance  of  the  carbon,  and  thus  ])roduce  corresponding  varia- 
tions in  the  induced  currents,  which,  acting  through  the  receiv- 
ing instrument,  reproduce  at  the  distant  station  whatever  has 
been  spoken  into  the  transmitting  instrument. 

For  lines  of  moderate  lengths,  say  from  one  to  thirty  miles, 
another  arrangement,  shown  in  flg.  106,  may  be  used  advantage- 
ously. The  induction  coil,  key,  battery,  and  receiving  and  trans- 
mitting telephones,  arc  lettered  the  same  as  in  the  previous  figure, 
and  are  similar  in  every  respect  to  the  apparatus  there  shown ;  the 
switch  S,  however,  differs  somewhat  in  construction  from  the  one 
akeady   described,  but  is   made   to   serve   a  similar  purpose. 


TEI-EI'IIONE   SIGNALLING   APPARATUS. 


229 


When  a  jiliig  is  inserted  between  8  ami  4,  tlie  relay  or  sovinder 
E',  battery  E,  and  key  K  only  arc  included  in  the  main  lino 
circuit,  and  this  is  the  normal  arrangement  of  the  apparatus  for 
signalling  purposes.  The  battery,  usually  about  three  cells  of 
the  Daniell  form,  serves  also  both  for  a  local  and  main  battery. 
"When  a  plug  is  inserted  between  1,  2  and  4,  the  apparatus  is 
available  for  telephonic  ctommunication. 

I  have  also  found,  on  lines  of  from  one  to  twenty  miles  in 
length,  that  the  ordinary  call  can  be  dispensed  with,  and  a  sim- 
plified   arrangement   substituted.     Tliis  latter  consists  simply 


of  the  ordinary  receiving  telephone,  Tipon  the  diaphragm  of 
which  a  free  lever,  L,  is  made  to  rest,  as  shown  in  fig.  107.  When 
the  induced  currents  from  the  distant  station  act  upon  the 
receiver  K,  the  diajihragm  of  the  latter  is  thrown  into  vibration, 
but  by  itself  is  capable  of  giving  only  a  comparatively  weak 
sound ;  with  the  lever  resting  upon  its  centre,  however,  a  sharp, 
penetrating  noise  is  produced  by  the  constant  and  rapid  rebounds 
of  the  lever,  which  thus  answ(>rs  very  well  for  calling  jjurposes 
at  stations  where  there  is  comjuiratively  but  little  noise. 


230 


THE   STKAKINIi   TEl.Kl'lli  iNK. 


Among  tlic  various  otlim'  m(>tli(i(ls  for  si<;;ii.illiiig  ])urposos 
wliicli  I  huvo  ex pori merited  witli,  I  may  mciilioii  tlio  sounding 
of  ii  note,  by  tliu  voice,  in  a  small  lieisss  tele[ili()nc;  the  emjiloy- 
mcnt,  of  11  seU'-vihrating  reed  in  the  local  circuit;  and  a  break 
wheel  with  many  cogs,  so  arranged  as  to  interrupt  the  circuit 
when  set  iu  motion. 


Rg.  107. 

I  have  also  used  direct  and  induced  currents  to  release  clock 
work,  iind  thus  operate  a  call,  and  in  some  of  my  earlier  acou.stic 
ex{)eriments  tuning  forks  were  used,  who.se  vibrations  in  front 
of  magnets  caused  electrical  currents  to  be  generated  in  the  coils 
surrounding  the  latter. 

By  the  further  action  of  these  currents  on  similar  forks  at  a 
distant  station,  bells  were  caused  to  be  rung,  and  signals  thus 


I" 


n. 


Fig.  108. 

given.  Fig.  108  shows  an  arrangement  of  this  kind.  A  and  B 
are  two  magnetized  tuning  forks,  liaving  the  same  rate  of 
vibration  and  placed  at  two  terminal  stations.  Electro-magnets 
m  and  m*  are  placed  opp.osite  one  of  the  p>rongs  of  the  forks  at 
each  station,  while  a  bell,  0  or  D,  stands  opposite  to  the  other. 
The  coils  of  the  magnet  are  connected  respectively  to  the  line 


ELECTRO-STA'l'lO   TKLEPUOXE. 


281 


wire  and  to  ciirlh,  Wlicu  one  of  tlio  forks  is  set  in  vibration  by 
a  sturtin;^'  kt-y  jn-ovided  for  tiio  pui'])os(,',  tiio  currents  produced 
by  the  apin'oarii  of  oik;  of  its  magnetized  prongs  towards  tla^ 
magnet,  and  its  recession  tiiercfroin,  pass  into  the  line  and  to  tiie 
furtlier  station,  whi'rc  tlieir  action  soon  causes  tlie  second  fork 
to  vibrate  witli  constantly  increasing  amplitude,  until  the  bell  is 


struck  and  the  signal  given. 


LJ3 


Fiij.  109. 

For  telephonic  calls  the  call  bells  arc  so  arranged  that  the  one 
opposite  to  the  fork,  wiiicli  generates  the  currents,  is  thrown  out 
of  the  way  of  tiie  hitter's  vibrations. 

Another  call  apparatus,  which  I  have  used,  is  represented  in 
fig.  109.  In  this  arrangement  two  small  magnetic  ])endnlums, 
whose  rates  of  vibration  are  the  same,  are  placed  in  front  of 


l^XE 


IT 


Fi<j.  110. 

separate  electro-magnets,  the  helices  of  -which  join  in  the  main 
line  circuit.  When  one  of  tin;  ]iendnlums  is  put  in  motion,  the 
currents  generated  by  its  forward  and  backward  swings  in  front 
of  the  electro-magnet  pass  into  the  line,  and  at  the  opposite  ter- 
minal, acting  through  the  helix  there,  cause  the  second  pendulum, 
to  vibrate  in  unison  with  the  former. 

Fig.  110  shows  a  form  of  elcctrophorous  telephone  which  acts 


232 


TIIK   Sl'KAKlNG   TELEl'IIONE. 


by  tlu!  approach  of  the  diaphragm  contained  in  ^V  or  B  towards 
or  its  I'ecession  from  a  highly  charged  eh'ctropiioroiis,  C  or  J). 
The  vibrations  of  tlio  transmitting  diaphragm  cause  a  (hsturbanco 
of  the  cliai'ge  at  botii  iMids  of  the  line,  an<l  tlnis  give  rise  to  faint 
sounds.  Pei'fect  insuhition,  liowever,  is  neeessni'v,  and  either 
apparatus  can  be  used  botli  for  transmitting  and  receiving,  but 
the  resuUs  arc  necessarily  very  wi'ak. 

Anotlier  form  of  elertrostatic  tek'phone  is  shown  in  fig.  111. 
In  this  ai'rangenient  Debic  jiiles  of  some  '20,0()()  disks  each  are 
containcil  in  ghiss  tubes  A  and  li,  and  conveniently  mounted  on 
glass,  wood  or  metal  stands.  The  diai)hragms,  which  an;  in 
electrical  connection  witli  the  eai'th,  are  also  j)laced  o])posite  to 
one  ]iolc  of  each  of  the  ])ilcs,  while  the  opposite  ])oles  are  joini^d 
togetlier  l)y  the  line  conductor.     Any   vil)ralion  of  either  dia- 


n.j.  111. 

phragm  is  thus  capable  of  disturbing  the  electrical  condition  of 
the  neighboring  disk.s,  the  same  jis  in  the  electrophorous  tele- 
2ihones  ;  and  con^  3(piently  the  vibrations,  when  ])rodueed  by  the 
voice  i'lone  instrument,  will  give  ri.se  to  corresponding  electrical 
changes  in  the  other,  ami  thereby  reproduce  in  it  what  has  been 
spoken  into  the  mouthjiiece  of  tin'  former. 

Whh  ihis  arrangement  fair  result.s  may  be  obtained,  and  it  is 
not  necessary  that  the  insulation  should  be  s  >  ]icrl'ect  as  for  the 
electrophorous  ajiparatu.s.  Fig.  112  shows  a  form  of  cleetro- 
mcchauieal  teleplnme,  referred  to  near  the  beginning  of  this 
eomnnmieatii)ii,  by  means  of  which  I  attempted  to  transmit 
electrical  impulses  of  variable  strength,  so  as  to  reproduce;  spokcMi 
words  at  a  dislani'c.  Small  resistance  <'oils — -1,  2,  l),  etc. — were 
so  arranged  with  connecting  s[)rings  near  a  jilatinmu  faced  lever 


:3 

THERMO-KLECTUIC   TELEPHONE. 


288 


B,  in  connection  with  tlic  diaphragm  in  A,  that  any  movement 
o[  the  latter  caused  one  or  more  of  tlic  coils  to  be  cut  in  or  out 
of  the  primary  circuit  of  an  induction  coil  C,  the  number,  of 
course,  varying  with  the  amplitude  of  tlie  vibrating  diaphragm. 
Iiubiced  currents  corresponding  in  strengtli  with  the  variations 
of  resistance  were  thus  sent  into  the  line,  and  could  then  be  made 
to  act  upon  an  ordinary  receiving  tele])lione.     By  arranging  the 


Fij.  112 


springs  in  a  sunflower  jiattcrn  about  a  circular  lever,  I  have  suc- 
ceeded in  transmitting  articulate  sentences  by  this  method,  l)ut 
the  results  wen;  very  harsh  and  disagreeable. 

Fig.  11.'^)  shows  a  form  of  the  water  telephone  ])rcviously  re- 
feiTcd  to,  in  which  a  double  cell  was  u.sed,  so  as  to  afford  con- 
siderable variation  of  resistance  for  the  very  slight  movements 


B 


Lim 


m 


Fig.  n.-?. 


of  t1ie  diaphragm.  The  action  of  the  apparatus  will  readily  be 
understood  from  the  figure,  where  a  win;  in  the  form  of  the; 
letter  IT  is  shown,  with  the  bend  attacheil  to  the  dia|)hi'agm,  and 
its  ends  flipping  into  tin;  sepanite  cells,  ami  thus  made  to  form 
part  of  lh(!  circiiit  when  the  lim^  is  joined  to  the  instrunn'ut  at  a 
anil  c. 

I  am  now  conduclnig  experiments  with  a  thermo-eleetric  tele- 


284 


THE   SPEAKING  TELEPHONE. 


])hone,  wliicli  gives  some  premise  of  becoming  serviceable.  In 
this  aiTaiigemeut  a  sensitive  tliermo-pile  is  placed  in  front  of  a 
diapliiagm  of  vulcanite  at  each  end  of  a  line  wire,  in  the  circuit 
of  which  are  included  low  resistance  receiving  instruments.  The 
principle  upon  whicli  the  apparatus  works  depends  upon  the 
change  of  temperature  produced  in  the  vibrating  diaphragm, 
whieli  I  have  found  is  iiiucli  lower  as  the  latter  moves  forward, 
and  is  also  correspondingly  increased  on  the  return  movement 

Sound  waves  are  thus  converted  into  iK'at  waves  of  similar 
characteristic  variation.s,  and  I  am  iu  hopes  that  I  mayultimat(;ly 
bo  able,  by  ihv.  use  of  more  sensitive  thermo-piles,  to  transform 
these  heat  waves  into  electrical  currents  of  sutricicnt  strength  to. 
])roduce  a  practical  tc]cj)hone  on  tliis  novel  iirineiplc. 

Before  concluding,  I  must  mention  an  interesting  fact  con- 
nected with  teleplionic  transmission,  wliich  was  discovered  during 
some  of  my  e.\i)eriinen1s  with  the  magneto-telejthone,  and  wliich 
is  this,  tliat  a  copper  disk  may  be  substituted  lor  the  iron  dia- 
phragm now  universally  used.  The  same  fact,  I  believe,  has 
also  been  announced  by  INfr.  W.  11.  Preecn;,  to  the  Physical 
Society,  at  London. 

If  a  piec(;  of  copper,  say  one  sixteenth  of  an  inch  thick  and 
three  fourths  of  an  inch  in  diamctei',  is  secured  to  the  centre  of 
a  \ideanite  diaphragm,  tlu;  effect  becomes  ipiitc  marked,  an<l  the 
ii]i[iaratus  is  even  more  sensitive  than  when  the  entire  diaphragm 
is  of  co|i|ier.  The  cause  of  the  sound  is  due,  no  doubt,  to  the 
Ijroduction  of  very  weak  electrical  currents  in  the  copper  disk. 


CHAPTER  VII. 


ELECTRO-HARMONIC   TELEGRAPIiy.  1 


Let  n.s,  in  imagination,  tran.spoi't  ourselves  backward  over  a 
period  of  three  centuries.  It  is  a  sumnn^r  evening  in  the  ancient 
ItaUan  City  of  Pisa — a  city  wliose  curious  leaning  tower  and 
inijtosiug  cathedral  liavc  T)ceu  rcckonccl  for  centuries  among  the 
arcliitectural  wonders  of  the  world.  Beneatli  tlie  lofty  ceiling  of 
the  great  cathedral  a  magnificent  central  cliandelier,  suspended 
by  a  sleiider  silver  cliain,  swings  slowly  to  and  fro  iu  the  gentle 
southern  l)recze  tliat  steals  tlu'ough  the  open  arclies.  From  his 
station  in  the  chancel,  idly  at  lii'st,  then  eagerly  and  intently,  a 
grave-faced  choir-hoy  follows  with  his  eyes  the  chist<  i'  of  glitter- 
ing lam[)s,  as  ever  and  anon  a  sudilcn  current  of  air  sets  it 
swinging  in  a  wide  arc,  and  then,  ceasing  for  ;i  time,  allows  the 
motion  to  die  away  iu  gradually  lessening  o-       it  ions. 

What  could  there  ha\"e  been  in  this  simple  ""cnrreuce  which 
so  interested  the  youthful  observer  in  the  chancel?  It  w;i-  this: 
lie  had  noticed,  what  doubtless  many  others  had  notice<l  before, 
but  without  in  the  least  apjjrehending  its  significance,  the  tact 
that  the  oscillations  of  the  suspended  chandelier,  whether  great 
or  small,  wen^  alwavs,  witlinut  exception,  perfornu'd  in  e([ual 
times.  Our  choir-boy,  although  a  mere  youth,  had  nevertheless 
alreadv  become  something  of  a  philosopher,  antl  his  snbseijuent 
rofii'ctions  upon  the  remarkable  fact  whicdi  had  thus  incidentally 
attracted  his  attention,  leil  hiiu  direetly  to  tlu;  disc  )very  of  one 
of  the  most  comprehensive  and  far-reaehing  of  all  physical  laws 
— the  law  of  isoclu'ouous  vibration  (the  word  isochronous  being 
derived  from  the  Grecik,  and  meaning  "  in  tvpial  times").  This 
discoverv  was  but  the  first  of  a  Ioult  and  l>rilliant  series,  v.'hich 


'A  paiuT  rc'iul  lu't'iiru  tlio  atiniiiil  luoetiiitf  i>f  tlio  AiiuMMciiii  Elooirioal  Society,  at 
(-liicaifo.  111.,  DiH'omlior  lii,  1877,  Ijy  t\  h.  I'opo.  Jouriial  of  tlio  Amoricuu  Klou- 
trieal  Sooicty,  vol.  i.,  No.  3. 


236 


THE   SPEAKING  TELEPHONE. 


have  justly  rendered  the  name  of  Galileo  forever  immortal  in  the 
annals  of  seicnco  and  of  history. 

In  order  that  wc  may  arrive  at  a  clear  understanding  of  the 
principles  underlying  tlie  dilfereut  varieties  of  the  telephonic, 
or,  in  more  general  terms,  the  electro-harmonic  system  of  teleg- 
raphy, and  that  we  lUiiy  be  ahle  to  trace  intx^lligently  its  origin 
and  development,  it  is  essential  that  we  should  first  l)ecorae 
s(Mnewhat  aerpiainted  with  the  laws  and  leading  phenomena  of 
vibratory  or  undnlatory  nioti(Mi  in  general.  Having  done  this, 
we  shall  find  no  dilheulty  in  ])assing  to  the  consideration  of  the 
special  practical  apjilications  of  these  laws,  which  have  recently 
been  made  in  the  domains  of  electro-telegraphy  and  electro- 
acoustics,  and  whii'li  have  Ijcen  attended  with  such  remarkably 
brilliant  and  successful  results. 

Let  us  consider  for  a  moment  some  of  the  peculiar  ])roperties 
of  a  body  freely  susjiended  from  a  fixed  point — in  other  words, 
a  pendulum,  i  sup})0se  there  are  not  many  here  present  who 
do  not  treasure  among  the  happiest  memories  of  childhood  the 
associations  connected  with  the  swing.  It  was  simply  a  seat 
suspended  l)y  two  ropes,  pei'hai)S  from  the  horizontal  branch  of 
some  overshadowing  tree.  I  shall  probably  bo  safe  in  assuming 
that  yon  all  have  a  tolerably  viviil  n^colleetion  of  most  of  the 
phenomena  presented  Ijy  this  mechanical  contrivance  when  in 
active  operation ;  a  \  itv  fori  iniaic  circumstance,  inasmuch  as  it 
will  enable  me  to  ])lacc  clearly  before  your  mind.s  some  of  the 
most  important  of  the  fumlameiital  laws  of  vibration. 


Wln'n  our  friend  ti 


10  scnoiili)ov.    navinii  sea 


ted 


out!    o 


f    hi.S 


youthful  fa\-orit(vs  in  the  swing,  ami  by  a  scries  of  judiciously 
timed  impulses  gradually  increased  the  amplitude  of  her  oscilla- 
tions from  zero  to  ])crliaps  120''  of  arc,  proceeds,  in  compliance 
with  her  breathless  reipu'st,  to  discontinue  his  exertions,  and,  in 
the  classic  language  of  the  play-ground,  to  ''  let  the  old  cat  die,'' 
it  is  hardly  sur[)rising  that,  not  being  aiii.uer  (ialileo,  our  young 
friend  has  utterly  faileil  to  grasp  the  great  ))hysical  ti'uth  that 
the  vibrations  of  the  little,  maiden  are  isochri)nous.  Still  h'ss 
does  he  probabl}'  suspect  that,  even  \'  en;  ho  to  subject  the  very 


PROPERTIES  OF  THE  PENDULUM. 


237 


pchoolma'ain  hcrsolf  to  tlic  same  conditions,  the  periodicity  and 
the  isoclironisni  of  lier  osciUations  would  not  difFcr  from  those 
of  her  predecessor,  notwithstanding  tlie  much  greater  weight  of 
the  oscillating  hody.  Nevertheless,  such  is  the  fact.  It  is  one 
whicli  was  experimentally  demonstrated  many  years  ago — ])y 
myself,  althougli,  of  course,  it  would  hardly  l)c  becoming  for  me 
to  claim  ab.solute  priority  over  all  others  in  making  the  experi- 
ment. 

Another  imj)ortant  property  of  tlie  pendulum  is  that,  by 
shortening  it,  it  oscillates  more  rapidly.  Thus,  if  we  take  two 
penduhims,  one  of  which  is  three  and  the  other  twelve  feet  in 
length,  the  shorter  pendulum  will  be  foimd  to  make  two  oscil- 
lations to  each  ono  of  the  longer  one,  and  if  wcs  continue  the 
experiment  with  ]>cndulums  of  difTercnt  lengths,  we  shall  arrive 
at  the  law  that  the  time  re([uirc(l  in  each  case  to  jierform  an 
oscillation  is  jjroportional  to  the  scjuare  root  of  the  length  of  the 
pendulum. 

I  will  also  call  attention  at  this  point  to  a  third  property  of 
the  vibrating  ])(;ndulum,  which  it  will  bo  very  important  for  ns 
to  remember,  in  view  of  what  we  shall  come  to  further  on;  a 
property  whicli  is  very  well  illustrated  by  the  suspended  swing, 
to  which  T  hax'c  just  referred.  It  is  this  :  A  freely  suspended 
body,  even  if  it  bo  very  heavy,  may  l)e  set  in  vibration  by  the 
rei)cated  application  of  a  comparatively  insignificant  force,  pro- 
vided tlic  successive  applications  of  the  force  1)0  properly  timed, 
but  not  otherwise.  Of  cour.se  you  hav(!  all  noticed  this  in  the 
case  of  the  swing,  and  therefore  I  need  not  enlarge  upon  it  fur- 
ther than  to  say  that  the  same  elTeet  is  ])roduced,  though  in  a 
less  degree,  no  matter  whether  the  impulses  are  given  at  every 
vibration,  at  every  alternate  vibration,  or  even  less  friMpiently. 
The  essential  condition  i.s,  that  the  intervals  of  time  between  the 
successive  iin[)ulseg  shall  be  exactly  the  same  as  the  intervals 
between  the  vibrations,  or  cLse  a  multiple  or  submultiplo  of  ono 
of  these  intervals. 

I  have  made  use  of  tho  suspcndeil  ]i(>ndulum  to  illustrate 
some  of  the  principal  laws  ot  vibratory  motion,  for  tho  reason 


238 


rilK    SI'KAKIN(t   'J'KI-KI'IIOXK. 


that  its  ]ilu'nomona  aro  faiiiiliar  to  y<m  all,  not  iiicn^lj  Leeaiiso 
they  aro  of  everv-day  (jccurrciico,  but  becauso  tlicv  aro  vcrv 
easy  of  comjjrchonsion  ])otli  by  tlin  vyo,  and  mind.  Hut  the 
laws  which  trovern  the  vibratiiiff  jx'iidulum  e(|nally  frovcni  al! 
the  A'aried  ])hascs  in  which  vibratory  motion  pn>si  nts  itsclt 
throughont  the  realm  of  physic*?!. 

All  solid  bodies  exhibit  the  ])henomena  of  vibration  in  various 
forms  and  degree.s,  aeeording  to  the  form  of  the  body  and  tlic 
manner  in  which  the  force  producing  tlie  vibration  is  ajiplicd. 
Cords  and  wires,  as  familiarly  seen  in  striiig(>d  instrument.s  of 
music,  have  their  elasticity  developed  by  tension  so  as  to  become 
capable  of  vibration.  If  tlie  cord  a  f  h  (iig.  114)  l)c  di-awn  out  in 
the  middle  to  rt  c  i,  upon  being  rehvised  its  elasticity  cau.'Jcs  it 
to  return  to  its  fornuT  ])osition.  The  velocity  of  this  movement 
is  constantly  accelerated,  and  is  at  its  maximum  when  the  cord 


Fig.  114. 

has  reached  its  line  of  equilibrium  afl;  consequently,  it  passes 
with  constantly  decreasing  velocity  to  a  d  h,  wlicre  it  eotnes  to 
rest  for  an  in.stant,  and  then  reti\nis  to  a  f  b,  and  so  continues. 
You  will  at  once  ])erceive  the  analogy  between  the  vibrations  of 
the  central  jioint  /  of  the  string  between  c  and  d  and  that  of  the 
weight  of  the  pendulum,  and  like  those  of  the  pendulum,  the 
vibrations  of  the  stretched  string  are  isochronous.  It  maybe 
regarded,  in  fact,  as  a  kind  of  double  jiendulum,  and  is  .subject 
to  the  same  laws  as  the  ordinary  pendulum.  The  tension  and 
diameter  being  equal,  the  number  of  vibrations  })erforme(l  by  a 
cord  in  a  given  time  are  inversely  as  its  length.  Elastic  rods 
vibrate  laterally  like  cords  when  fixed  by  their  extremities.  In 
conse(iuence  of  tluMr  rigidity,  however,  they  may  be  made  to 
vibrate  when  fixed  only  at  one  extremity.  Thus,  a  straight  steel 
rod  n  0  may  be  chuiiped  iu  a  vice,  as  shown  in  Iig.  115.    If  we  draw 


VIBRATINft  noi)>'. 


239 


tho  free  nid  71  aside  and  tlion  lihoralc  it,  it  will  vibrate  to  and 
fro  between  the  jioints  p  and  ]?  as  sliown  by  the  dolled  lines. 
Tho  am[)litude  of  tho  successive!  vilirations,  liowcvcr,  constantly 
diminishes,  until  at  len,irth  the  r<>d  returns  to  its  original  stale  of 
rest.  Sueli  a  rod,  when  vibrating,  follows  the  same  law  as  the 
pendulum  and  tlio  stretched  c(m\,  each  vibration,  whether  greater 
or  smaller,  being  performed  in  tho  same  lengtb  of  time,  and  the 
number  of  vibrations  in  a  givi'u  time  b<'ing  iuversely  propor- 
tional to  the  square  of  tho  length  of  tko  rod. 

P 


Fig.  115, 


Fig.  tie. 


The  onlinary  tuning  fork,  an  almost  indispensable  instrument 
in  the  experimental  investigation  of  tho  various  ])roblcms  of 
acoustics,  consists  virtually  of  a,  doidde  vibrating  ro<l  of  the  above 
character.  As  actually  constructed  il  is  simply  a  steel  bar,  bent 
into  the  form  of  an  elongated  letter  U,  and  supported  or  clamped 
at  the  midille  of  the  bt'nd,  leaving  the  extremities  free  to  vibrate. 
Wh(ni  such  a  fork  is  struck,  and  thrown  into  viliratiDU  so  as  to 
sound  its  deepest  note,  its  freo  end  osi^illates,  as  seen  in  lig.  116, 


240 


THE   SPEAKING  TELEI'HONE. 


where  the  proncrs  vibrate  hctwccii  tlio  hniits  b  n  and/Tw,  p  and 
q  being  points  of  no  vibnitioii,  tcrrned  nodcs.^ 

Elastic  pLites  arc  easily  thrown  into  vibration,  but  the  charac- 
ter of  their  vibrations  depends  upon  the  conllguration  of  the 
plate,  the  manner  in  Avhich  it  is  snp|)orted  or  clamped,  and  the 
point  at  Avhich  the  exciting  or  moving  force  is  applied.  For 
example,  a  circular  plate,  or  a  plate  of  any  regular  geometrical 
figui'c  capable  of  being  circumscribed  about  a  circle,  which  is 
clamped  or  stojipcd  at  the  edges,  but  otherwise  free  to  viln-ate, 
will  have  no  decided  tendency  to  any  given  rate  of  vibration,  but 
will  respond  to  any  kind  of  vibrations  which  may  be  (communi- 
cated to  it.  But  if  the  plate  be  elongated,  the  normal  rate  of 
vibration  is  affected  by  the  length  of  tlie  ])late,  without  reference 
to  its  breadth.  The  greater  the  length  of  the  ])late  in  proportion 
to  its  breadth,  the  more  it  partakes  of  tlie  character  of  an  elastic 
rod  or  a  stretched  string,  according  as  it  is  supported  at  one  or 
both  ends,  and  tlu>rtby  becomes  caj)able  of  vibrating  at  one  par- 
ticular rat(!,  and  no  other.  You  will  see,  therefore,  that  wo  may 
have  a  succession  of  plates  of  various  forms,  passing  by  degrees 
from  the  circular  ])late  clarniicd  at  its  edges,  which  will  take  any 
rate  of  vibration  with  e(jual  facility,  to  the  string  f)r  rod  clamped 
at  one  or  both  ends,  which  will  only  take  one  particular  rate, 
rejecting  all  others.  These  properties  of  plates  of  diiferent 
forms,  in  ncsjici't  to  their  modes  of  vibration,  are  of  tho  utmost 
importance  in  harmonic  telegraphy,  as  we  shall  hereafter  see. 

It  renuiins  to  speak  of  the  vibrations  of  membranes,  which  are 
in  iTiany  respects  analogous  to  those  of  ])lates.  "When  loosely 
stretched  over  a  circidar  liooj)  or  frame,  such  a  Tnembranc,  like 
tho  circular  ])late,  has  no  decided  tendency  to  vibrate  at  any  ])ar- 
ticular  rate.  If  strained  more  tightly,  however,  its  tendency  to 
vibrato  at  .somes  particular  i-ate  is  increased. 

Omitting  for  the  pnssent  a  inore  })ailieidai*  consideration  of 
the  characteristics  of  vibrating  solids,  we  will  now  examine 
the  effects  of  vibratoiy  motion  upon  fluids. 


Tyinlull — "  Lucturi's  on  Sound"  (Anicriciiii  edition),  ji.  ISS. 


VIBKATORY    MOTION   OF   KIJ'IDH. 


241 


If  we  drop  a  smooth,  round  pebble  into  the  bosom  of  a  placid 
pool,  a  series  of  concentric  undulations  are  produced.  Wave 
follows  wave,  in  ever-widening  circles,  until  opp(Jsing  forces  at 
length  cause  an  equilibrium  to  bo  regained.  At  the  initial  point 
a  depression  is  produced  by  the  fall  of  the  pebble.  Around  this 
there  first  rises  a  circular  elevation  above  the  surface  of  the 
liquid  when  in  equilibrium,  and  immediately  beyond  this  is  a 
circular  depression,  and  so  on,  altciiuitely,  successive  elevations 
and  depressions.  When  we  look  at  this  progressive  series  of 
waves,  the  entire  mass  appears  to  advance  progressively  in  every 
direction  away  from  the  ])oint  of  excitation;  but,  if  wc  watch 
the  movements  of  some  light,  flouting  body,  we  shall  sec  that 
this  body  is  not  carried  forward  over  the  surface,  but  merely 
rises  and  falls  alternately  as  the  waves  pass  beneath  it.  ^Nforc- 
over,  wc  shall  bo  able  to  observe  an  exact  analogy  between  the 
vertical  oscillations  of  this  floating  body  and  those  of  the  sus- 
jiended  weight  of  tho  pendulum,  or  the  central  point  of  the 
stretched  string,  thus  proving  that  the  vibratory  motion  which  we 
have  already  exnniined,  and  the  undulatory  motion  uiuhsr  con- 
sideration, are  manifestations  of  the  same  law  under  difTerent 
conditions. 

The  undulations  which  wc  have  just  described  are  surface 
waves.  All  elastic  mediums  are  also  subject  to  undulations  of 
a  totally  dillerent  character,  which  are  termed  waves  of  conden- 
sation and  rarefaction,  and  are  produced  in  air  and  gases  by  any 
disturbance  of  density.  If  any  elastic  fluid  be  compressed,  and 
then  suddenly  released  from  compression,  it  will  exjiand,  and  in 
its  cx2)ansion  exceed  its  former  volume  to  a  certain  extent,  after 
which  it  will  again  contract,  and  thus  oscillate  alternately  on 
either  side  of  its  position  of  rest  It  must  be  understood  that 
this  class  of  nndulations  extend  equally  in  every  direction  from 
a  centre  toward  every  point  of  tho  circumference  of  a  sphere. 
This  alternate  condensation  and  expansion  of  an  elastic  fluid  or 
medium,  extending  spherically  around  the  original  centre  of  dis 
turbanee,  is  perfectly  analogous  to  the  series  of  cinndar  wavc-i 
which  wc  have  seen  formed  around  a  point  of  depression  on  the 


242 


THE   HPEAKIX(}   TKIiEl'HONK. 


i 


surface  of  a  liquid,  tlic  cuiKlcnsatioii  of  tlie  clastic  fiiiid  corre- 
sixiiuling  to  the  elevation  of  a  surface  wave,  ami  the  phase  of 
rarefaction  correspondinif  to  the  jihaso  of  <lepn>ssi()n. 

Suppose  liji".  117  to  represent  a  section  of  a  s])here  of  air,  or 
other  elastic  mcdinni  in  whicli  the  waves  of  condensation  ami 
rarefaction  have  extended  outward  from  the  centre  (-,  tiien  the 
heavy  lines  aefy,  h  h  ik  ami  d  I])  q,  will  represent  the  phases  of 
greater  condensation,  the  finer  int(>rniediate  lines  will  represent 
the  spaces  of  greatest  rarefaction,  and  the  distances  vi  n  and  n  o, 
h(>tw(^en  circles  of  greatest  condensation,  will  be  the  length  of 
the  waves. 


Fig.  m. 

These  waves  of  condensation  and  rarefaction  in  an  elastic 
medium,  like  the  waves  on  the  surface  of  a  licpiid,  are  subject  to 
the  ordinary  laws  of  vibration,  and  are  capable  of  producing  or 
of  being  produced  by  the  vibrations  of  a  soliil  body. 

The  nnitual  eonvertiliility  of  vibrations  and  undulations  may 
be  shown  by  c.\})crinicnt.  If  a  tuning  fork  is  stnick  or  e.xcited 
])y  a  violin  bow  and  its  motion  allowed  to  gradiially  die  away, 
its  prongs  oscillate  backward  and  fm-ward  in  the  same  manner 
and  after  the  same  law  as  a  pendulum,  except  that  they  make 
niany  hundred  vil)rations  for  each  single  A'ibration  of  the  jmmuIu- 
bim.  A  jiarticular  tuning  fork,  therefore,  will  always  perform  a 
given  number  of  vibrations  in  a  unit  of  time.     This  number  de- 


(t 
sa 
ti< 
nn 


hu 


VELOCITV   OK   SolNl). 


243 


pends  pf>lel\'  ujiori  tlio  constrimlioii  of  tlic  fork,  fiixl  ciiii,  there- 
fore, neitlicr  lie  iiicrcasv'tl  iior  diiniuishfil,  unless  IIk;  form  or 
properties  of  tlio  fork  are  in  Homo  way  cliuuged. 

If  we  tlirovv  siieh  a  t\uiin<^  fork  into  vibration  tlie  vilirations  of 
llie  fork  cause  undnlatious  in  tlio  surrounilinL'  aii'.  whiili  uro.  pro- 
2)aj:ate(l  in  every  diri'i'tioii.  TTow  is  tliis  broni^lit  about,?  Kacli 
of  the  ^jron^rs  licats  tlie  air  in  o[)posito  directions  at  the  same 
time.  Let  us  try  to  jiicturo  to  ourselves  the  jihysical  condition  of 
the  air  in  front  of  one  of  tlicse  ])rougs.  As  thtilattiir  strikes  out- 
ward the  air  in  front  of  it  will  he  driven  outward,  condensed,  and 
on  account  of  tlio  elasticity  of  the  air,  the  comhmsatiou  will  at 
once  start  to  trav<4  outward  in  every  direction  a  wave  of  denser 
air;  hut  directly  the  prong  recedes,  heating  the  air  hack  in  the 


Fig.  118. 

contrary  direction,  which  will,  of  course,  rarefy  the  air  in  front 
of  tlie  prong.  But  the  disturhanco  wo  call  a  rarc^factioii  is 
])ropagated  in  aii"  with  the  saino  velocity  as  a  condiMisation. 
We  nust  therefore  renicmher  that  just  behind  the  wave  of  eon- 
dens^jtion  there  is  a  wave  of  rarefaction,  each  travelling  with  the 
same  velocity,  and  then^fore  always  maintaining  the  same  ])osi- 
tion  in  relation  to  each  other.  'JMins  the  foi'k  vibrates  a  certain 
number  of  times  in  a  .second,  and  will  consequently  generate  an 
equal  number  of  these  waves,  all  constituted  alike  and  the  same 
length.  (See  fig.  lis.)  Suppose  a  fork  to  make  one  hundred  vi- 
brations ])cr  second:  at  the  end  of  the  first  s<'cond  the  wave 
geiierateil  by  the  vibration  at  the  beginning  of  the  second  would 
liavo  travelled,  say,  eleven  hundred  feet  (which  is  known  to  be 


244 


THK   SI'KAKINa   TELEl'HONK. 


approximately  tlic  distance  traveraed  in  a  Hecond  by  aerial  vibra- 
tion), and  tlio  intcnncdinti!  \vavc?(  would  be  nnifi)rmly  distributed 
over  tlie  int(^rveuing  distani'(! ;  tliat  is  to  say,  in  eliiven  Imndrcd 
feet  there  would  be  one  liundnul  waves,  each  of  them  evidently 
being  eleven  feet  in  length.  IP  tiie  fork  made  elcjvcn  hundred 
vibrations  jier  second,  each  of  these  waves  would  be  oiu;  foot  long, 
for  waves  of  all  lengths  traverse  the  air  with  precisely  the  same 
velocity.! 

Now,  if  we  })lace  in  another  ])art  of  the  same  room  aiiotlun' 
fork,  so  constructed  as  to  make  exactly  iho  same  Jinnil)er  of 
vibrati(ms  per  second  as  the  first  one,  and  set  the  first  one  in 
vibration,  the  other  one  will  soon  begin  to  vibrate  in  sympathy, 
and  it  will  even  continue  to  vibrato  after  the  first  one  had  l)eeu 
.stopj)ed.  Astonishing  as  it  seems,  it  is  nevertlailess  true;  that 
this  heavy  and  rigid  mass  of  steel  has  been  set  in  motion  merely 
by  the  successive  impact  of  hundreds  of  tiny  waves  of  air,  each 
of  sueli  small  motive  power  that  it  could  not  stir  the  weakest 
spring  which  was  not  adjust d  in  unison  with  the  fork.  Tim 
slightest  disagreement  in  the  respective  rates  of  vil)rations  of  the 
two  forks  sensibly  diminishes,  and  a  dilTerenee  of  one  vibration 
in  two  or  three  hundred  2)er  second  wholly  destroys,  the  cffeet. 

Thus  we  SCO  that  the  isochrf)nous  vibrations  of  tlu;  tirst  fork 
give  rise  to  corresponding  waves  or  nndulations  of  condensation 
and  rarefaction  in  the  air,  and  these  in  turn  rei)roduco  isochron- 
ous vibrations  in  the  second  fork,  and  will  also  produce  vibra- 
tions to  a  greater  or  l(;ss  extent  in  every  body  which  is  capable 
of  vil)rating  in  unison  with  the  first  fork. 

Thus  far  we  have  confined  our  attention  solely  to  the  nature 
and  effects  of  simple  vibrations.  It  remains  to  consider  what 
effect  is  ])ro<luced  when  a  nundier  of  distinct  sets  of  vibrations 
are  simultaneously  propagated  through  the  same  medium. 
Before  attempting  to  explain  this,  it  is  d(;sirable  that  we  should 
understand  the  gra})hical  method  of  delineating  vibratory  and 
other  motions  which  mathematicians  and  phyicists  are  accus- 


i  Dolbear— "  Tho  Telephone,"  p.  OS. 


GUAl'lllCAIi    METHODS   OK   I'lIVSICISTS. 


245 


tomcd  to  employ  in  oi'dcf  to  yhivr.  tlie  cliaraeteristics  of  these 
motions  before  tlio  iriind  tliroii^^h  tlio  iiKid'miu  of  the  eye,  in  a 
manner  much  more  inlolligil)lc  than  i.s  possible  even  by  the  most 
minnto  verbal  description. 

Suppose  we  liavc  a  pendulum  swinging  from  right  to  left  and 
left  to  right  with  a  uniform  motion.  In  the  vicinity  of  either 
end  of  its  ])ath  it  moves  slowly,  and  in  the  middle  much  more 
rapidly.  If  we  should  attach  a  2)eneil  to  the  end  of  the  pendu- 
lum-rod so  that  it  would  mark  upon  a  contitmous  slip  of  ])aper  of 
sufficient  width,  moving  uniformly  beneath  it  at  right  angles  to 
the  plane  of  its  oscillation,  a  wavy  line  would  be  ])roduced. 
This  wavy  line  once  drawn  wouiil  remain  as  a  j^ormancnt  record 
of  the  kind  of  motion  ])erformed  by  the  pendulum  during  evcy 
j)art  of  its  oscillation.    Fig.  119  represents  a  line  such  as  would  be 


Hg.  119. 

produced  by  the  process  we  have  just  described.  It  is  not  difli- 
oult  to  comprehend  the  meaning  of  the  curves  which  are  tlius 
formed.  The  marking  ])oiiit  has  passed  relatively  to  the  paper 
with  a  uniform  velocity  in  the  direction  a  d.  Suppose  it  has 
described  the  section  ac  in  f)ne  second.  Divide  a  c  into  twelve 
equal  ])arts,  as  in  the  figure,  then  the  ])oInt  has  been  one  twelfth 
of  a  second  in  describing  the  horizontal  length  of  any  one  of  these 
divisions,  and  the  curve  shows  us  on  which  side  and  at  what 
dist;ineo  from  the  position  of  rest  the  vibrating  point  will  bo  at 
the  end  one  twelfth,  two  twelfths,  and  so  on,  of  a  second  or  gen- 
erally at  any  given  short  interval  of  time  after  it  lias  left  the 
point  a.  Wo  sec  in  the  figure  that  after  one  twelfth  of  a  second 
it  had  reached  the  height  1,  and  that  it  rose  gradually  till  the 
end  of  three  twelfths  of  a  second ;  then,  however,  it  began  to 


246 


TllK   SPEAKIXa  TELEPHONE. 


descend  gradually,  till  at  tlio  end  of  t^ix  twelfths  of  a  second  it  had 
reaehml  its  :.iean  ])()siti()ni,  and  then  it  continued  d(!Scendingon 
the  o])posite  side  till  tlu;  I'tid  of  nine  twelfths  of  a  second,  and  so 
on.  We  can  also  easil}'  determine  where  tlie  vibratory  point 
was  to  be  found  at  the  end  of  any  fraction  of  this  twelfth  of  a 
second.  A  diagram  of  this  kind,  tlierefore,  shows  at  a  glance  at 
what  point  of  its  path  a  vibrating  particle  is  to  be  found  at  any 
given  instant,  and  thus  gives  a  complete  image  of  iio  motion.^ 

Although  wo  are  i)f)t  yet  able  to  make  all  vibrating  bodies 
automatically  record  their  movements  on  paper  in  this  manner, 
yet  we  may  ourselves  constrnct  curves  vliicli  trutlifully  represent 
their  vibration  ■when  the  law  of  their  motion  is  known;  that 
is,  when  wo  know  how  far  tlie  vibrating  })oirit  will  bo  from  its 
mean  position  at  any  given  moment  ot  time.  We  set  oil  on  a 
horizontal  line,  such  as  a  h,  fig.  119,  lengths  corresponding  to  the 
interval  of  time,  and  let  fall  per])endicnlars,  or,  in  matliematical 
language,  ordinatcs  to  it,  <ui  either  .side,  making  their  lengths 
equal  or  2)roportional  to  the  distance  of  the  A'ibrating  jioint  from 
its  mean  position,  and  then  by  joining  the  extremities  of  these 
perpendiculars,  we  obtain  a  curve  .«uch  as  tlio  vibrating  body 
"would  actually  have  drawn,  if  it  had  been  possible  to  make  it  do 
so.  Physicists,  tlierefore,  having  in  tlieir  minds  such  curvilinear 
forms,  re])resenting  the  law  of  the  motion  of  vibrating  bodies, 
are  aciuistomed  to  spe.ik  as  a  matter  of  conveniinicc  of  the  form 
of  vibration  of  such  bixlics,'^  a  term  whie''  I  shall  hereafter 
employ  Avhen  referring  to  tlu;  subject. 

Wo  are  now  ready  to  return  to  the  consideration  of  the 
pheuom<'na  of  compound  vibration.-;.  ^I'o  illustrau;  in  a  general 
■way  tlie  ciiaractcristics  of  this  kind  of  motion,  we  conveniently 
refer  again  to  the  "waves  formed  upon  a  calm  surface  of  water. 
We  lia\e  seen  that  if  this  surface  is  agitated  by  a  pebble  dropped 
upon  it,  tliat  the  agitation  is  ])ro2)agated  by  concentric  waves 
extending  in  every  direction  from  tiie  centre  to  a  greater  and 


I  ITilinlioltz — I'ULehre  von  d<n  'JoriemjtfinJuniH'n.  iKw^Vi^h  TninsUitinM,  l.y  A.  .T. 

Ellis  I,  J..  ;u. 
2  Ibia.,  ji.  r,'j 


PROPAaATION   OF   COMPOl'Nl)   VIBRATIOXS. 


247 


greater  distance.  Now,  if  we  drop  two  [lebbles  at  two  points 
some  little  distanec  from  each  other,  wo  shall  ]troducc  two 
■se]iarate  centres  of  agitation.  Each  will  set  in  motion  a  separate 
sot  of  concentric  waves,  and  these  two,  gradually  exjjanding, 
will  tinally  meet  and  overlap  ea(!h  .)thor.  When  tlii.s  happens, 
it  is  easy  to  soi;  that  not  only  the  water,  hut  any  floating  body 
upon  its  sarfac(!  as  well,  will  be  sot  in  motion  by  both  kinds  of 
agitation  at  the  same  time,  but  this  fact  will  in  no  wise  hiterfere 
with  the  .separate  propagation  of  both  sets  of  waves.  Each  of 
these  will  continue  to  advance  further  and  further  over  the  sur- 
face precisely  as  if  the  other  had  no  existence.  As  tluy  jiro- 
ceed,  those  parts  of  both  rings  which  have  just  coincided  ajjpear 
again,  distinct  and  unchanged  in  form.  Those  little  systems  of 
waves  may  be  accompanied  by  other  and  larger  systems,  caused 
by  the  action  of  the  wind,  but  they  will  continue  to  spread  out 
over  the  surface  thus  agitated,  with  the  same  systematic  regu- 
larity that  thijy  did  upon  a  perfectly  c.ihu  r^n. '■•"c. 

The  action  of  the  vibrations  or  undulation**  "f  iiio  atmosphere, 
which  produce  the  sensation  of  sound,  is  strictlv  analogous  to 
that  of  the  waves  of  water.  There  is  practically  nc»  limit  to  the 
number  of  distinct  sets  of  vibrations  which  maybe  going  on  at 
the  san>o  time,  without  mingling  with  each  other;  but,  in  cases 
where  there  are  many  <if  these,  the  resulting  motion  of  each 
separatt^  ))articK'  of  air  is  necessarily  complex,  almost  beyond  the 
power  of  the  mind  to  conceive.  The  principle,  however,  may 
be  understooii  perfectly  well  by  studying  the  composition'of  two 
or  three  sets  of  simple  vibrat  '>ns,  and  this  may  bo  readily  done 
by  the  aid  of  the  method  of  graphie  pri^jection,  which  has  been 
before  ex[)lained. 

Tims  in  lig.  120,  wo  may  suppose  th  ;  horizontal  length  of  the 
diagram  to  represent  a  unit  of  time.  The  curve  A  will  then 
re[)rosent  tin;  undulation  in  the  atmosphere  caused  by  the  vi- 
brations of  a  tuning-fork  in  acticui.  The  horizontal  <listances 
measured  on  the  straight  line  will  represent  the  passing  time, 
and  the  vertical  luMghts  the  corresponding  displacements  of  the 
particles  of  air.     Now,  suppose  a  second  fork  is  set  in  action, 


248 


THE   SPEAKING   TELEPHONE. 


which  is  tuned  an  octavo  higher  than  the  first,  and,  conse- 
quently, makes  U\'ico  as  many  vibrations  in  the  sanietimc.  The 
undulations  produced  by  the  second  fork  will  be  represented  by 
the  curve  B.  In  such  case,  the  curves  above  the  horizontal  line 
repres(!nt  the  conii)ression  of  the  air,  and  those  below  the  line 
its  rarefaction.  Now,  according  to  the  laws  of  mechanics,  if  two 
different  forces  act  in  the  same  direction,  the  total  force  is  repre- 
sented by  their  sum,  while  if  they  act  in  opposite  directions  it  is 
represented  by  their  difference.  If,  therefore,  we  comlMiie  these 
two  sim])le  curves,  according  to  this  principle,  we -shall  have  a 
composite  curve  C,  which  represents  the  effect  produced  by  the 


Fig.   120. 

superposition  of  one  set  of  waves  upon  another.  The  lino  Cj 
is  the  sum  of  the  lines  ffj  and  Jj,  while  Cj  is  exactly  equal  to 
«3.  On  tho  other  hand,  the  lino  c^  represents  the  difference 
-between  tho  lines  O3  and  b^,  one  being  above  tho  horizonUxl  line 
and  tho  other  below  it.  Every  point  in  tho  curve  C  may  bo 
f(nind  in  tho  same  manner,  and,  by  tho  same  method  of  con- 
struction, the  resultant  curve,  corresponding  to  any  numlxn'  of 
sitn])le  curves  combined  togethei',  may  also  b(!  found,  as  you  will 
readily  understand. 

Tho  simplo  vibrational  form  is  ulways  the  same.     Tt  is  oidy 


i^ 


FOURIER  S   LAW    OF    VIBRATIONAL   FORMS. 


249 


it«?  wav(^  height  or  amplitiulo,  and  its  wave  leiigtli  or  periodic 
time,  wliieli  is  snsccptihlo  of  (change.  But  the  number  of  vibra- 
tional forms  which  may  arise  from  the  composition  of  simple 
forms  are  lathematically  infinite.  Tlie  converse  of  this  prop- 
osition is  also  true,  which  is,  that  any  form  of  vibration,  no 
matter  how  complex,  maybe  expressed  as  the  sum  of  simple 
vibrations.  '^i'liis  was  fii'st  mathematieall}''  demonstrated  l^y 
Fourier,  but  its  experimental  proof  is  due  to  the  labors  of  the 
^ great  German  physicist,  llelmholtz,  who,  after  a  most  elaborate 
series  of  investigations,  succeeded  in  separating  from  each  other 
the  several  simple  sounds  which  form  the  constituents  of  a  com- 
posite sound.  It  is  not  necessary  here  to  enter  into  a  description 
of  the  methods  empl(>\'ed  ])y  Jlclmliolt/.  in  accomplisliing  this 
beautiful  result,^  although  we  shall  luive  occasion  to  refer  here- 
after to  some  of  the  analogous  means  which  have  been  employed 
in  telegraphy  for  the  same  purpose,  that  is  to  say,  the  analysis  of 
C(jmposite  ■sibratory  motion.s. 

The  idea  of  synchronizing  the  movements  of  the  two  instru- 
ments at  wi'^'ly  sejiaratccl  points  for  telegra})hi<!  jiurposes  by 
making  use  of  the  jiriueiples  of  isochronous  vibration,  was 
em})loycd  in  telegraphy  at  a  very  early  period.  Thus  Eonalds^ 
in  1861,  and  Vail'  in  1837,  employed  isochronous  pendulums 
to  control  their  machinery,  while  at  a  later  date  the  printing 
telegrajih  of  Hughes,'*  and  the  automatic  telegraiih  of  Casselli 
and  others,  have  embodied  most  ingenious  and  beautiful  appli- 
cations of  the  same  principle,  with  which  I  })rcsumo  you  arc  all 
more  or  less  familiar,  and  therefore  I  need  not  dwell  upon  them. 

In  1861,  ^fr.  PliilipReiss,  of  Germany,  made  the  first  apparatus 
of  which  we  have  any  account,  for  reproducing  musical  sounds 
at  a  distance,  bv means  of  electro-magnetism.      His  devic(>s  were 


1  For  ft  full  ftoconnt  of  tlio  iiiipiirutus  iindinctliods  emiiloyeil  in  tlieno  cxperlmoiits, 
sen  il)ul.,  Clmiitrr  III. 

»  So«  .SliaH'MiT  -"TcU'trrapli  Miinniil,"  ]..  117. 

'  Vail — "Eloctro-iuu){iiotio  Toloj^rupli,"  ji.  l.'^'i ;  Sluilfrirr  -"  Tuloi^rupli  Maimiil," 
p.  .182. 

•1  Prcspott  — "  History,  Tlnnry  ami  Pruotlco  of  Klfclrii'  Tilt'tfraiili,"  \k  1".',i.  A1»u 
saiiK!  aiithor'.H  "  Klut'trii.'ity  anil  Klcctno  IV'K'jirai'li."  i<.  i>"\). 


260 


THE  SPEAKING  TELEPHONE. 


very  ingenious  and  beautiful,  and  it  is  cvidonl ,  f rom  doscriptions 
and  ])aj)ers  published  at  that  tiniu,!  ono  of  which  lias  recently 
been  reproduced  in  the  Journal  of  the  lVlegra[)h,  that  Reiss  had 
made  a  thorough  study,  both  of  the  laws  of  electro-magnetism 
and  of  acoustics,  and  nndcrstood  perfectly  the  conditions  of  the 
problem  with  which  he  undertook  to  deal. 

Sound  is  simply  a  sensation  resulting"  fnmi  the  action  of 
vibrations  upon  the  nerves  of  the  ear.  If  the  same  vibrations 
are  felt  by  the  touch,  they  ]iroduce  a  certain  i)cculiar  lluttcring 
sensation  ;  but  this  is  not  sound.  Therefore,  although  all  souud.s 
arc  neces'-arily  the  result  of  vibrations,  all  vibrations  do  not 
necessarily  produce  sound.  The  vil)ratory  motions  proceeding 
from  soundiny  bodies  are  nsuallv  couducted  to  the  ear  throiiy;!! 
the  medium  of  the  atmosphere,  '^i'liercfore,  to  produce  any  given 
sound,  of  whatever  characti'r,  at  a  distance,  it  is  evidently  only 
necessary  to  throw  the  atmosphere  at  tiiis  point  into  vibration 
precisely  similar  in  every  respect  to  those  which  wouhl  be  ]->ro- 
duced  by  the  action  of  the  original  source  of  sound,  whatever  it 
may  be. 

It  is  found  that  all  ilw.  characteristics  of  souml  which  are 
appn-ciable  by  our  senses  depend  upon  three;  things:  Kirst,  the 
rapiility  of  tlu;  vibrations,  which  determines  what  we  call  the 
pitch  of  the  sound,  whether,  for  example,  it  is  high  or  low; 
second,  the  aniiilitude  of  the  vibrations,  wiiich  determines  the 
loudness  or  power  of  the  sound  ;  and,  third,  tlu!  form  of  vibra- 
tion, as  ri'presentcd  by  tlu;  curve  corresponding  to  the  movement 
of  the  vibrating  body,  which  determines  the  (piality  of  the 
sound. 

The  apparatus  of  R;'iss  consisted  of  a  thin,  stretched  mem- 
brane, rigidly  supijortcd  at  tlu;  edges,  and  free  to  vibrate;  in  iIh; 
middle.  Tiie  mathematical  theory  of  the  vibration  of  such  a 
membrane,  having   a  uniform  tension  in  all  directions,  shows 


1  K"isa— Piiiftlor'H  /hli/tfi-Jinie  Journal,  WA.  n.XVIII.,p.  is.l ;  T.t'^iit  Zntucftrift 
df>  JhiitsfhiiKtirreichinelien  'JUi'irajilien  IV/v/h*,  Vol.  I  \'.,  ]i.  l'J."i.  An  (.'Xi'i'llciit  trii'iH- 
liitioii  of  this  lust  jiujiur  may  lio  I'ouiiJ  in  thu  Journal  of  the  Tehijraph^  Vol.  X.,  p. 
8S3. 


BEISSS  APPAHATUS. 


251 


tliat  vibrations  produced  in  any  part  of  the  membrane  will  pro- 
duce nearly  as  strong  vibrations  (disregarding  individual  nodal 
lines)  in  all  other  parts  of  it  A  thin,  light  membrane  is  not 
only  susceptible  of  sympathetic  vibration  when  vibrating  air  is 
allowed  t(i  act  upon  it,  but  this  vibration  is  not  limited  to  any 
particular  pitch,  and  it  is  therefore  capable  of  respDuding  to 
sonorous  vibrations  of  every  character,  traversing  the  atmos- 
phere. A  delicate  circuit-breaker,  attached  to  the  membrane, 
was  arranged  to  break  the  circuit  of  a  telegraph  line  at  the 
vibration,  and  thus  the  armature  of  an  electro-magnet  at  the 
receiving  station  was  easily  adjusted  to  respoiul  to  those  vibra- 
tions, and,  when  moiniied  upon  a  proper  sounding-board,  gave 
them  out  to  the  atniosjjhere,  which  conveyed  them  to  the  ear  of 
the  listener. 

Now,  if  the  form  of  vibration  in  this  sounding-board  could 
have  been  made  to  coincide  in  all  respects  witli  that  of  the 
membrane  at  the  station  from  which  the  vibrations  had  been 
transmitted,  Reiss  would  have  had  a  jierfeet  .sound  telegrajdi  or 
telephone.  But  this  was  fur  from  being  the  case.  The  pitch 
and  rhythm  of  the  sounds  were  perfectly  preserved  ;  their  loud- 
ness or  intensity,  also,  to  a  very  small  extent;  but  the  quality 
was  entirely  lost.  It  is  notdiflicult  to  understand  the  reason  of 
this.  Kvery  vibration  of  the  membrane  caused  a  pulsation  of 
electricity  to  traver.sc  the  wire  and  act  upon  the  electro-magnet, 
but  as  each  and  every  vibration  of  the  armature  was  produced 
by  a  current  of  jn'ci-isely  the  same  strength,  the  oidy  difference 
in  the  amplitude  of  these  vibrations  would  be  that  due  to  the 
more  complete  magnetization  or  demagnetization  of  the  electro- 
magnet, when  the  time  allowed  for  the  jjrocess  was  increa.sed  by 
ihe  greater  ^ilay  of  the  circuit-closer,  under  the  inlluenc(^  of 
stronger  vibrations  at  tin;  transmitting  station.  The  form  of  the 
vibrations  was  of  course  altogether  lost.  Any  simple  musical 
lone,  consisting  of  a  regular  succession  of  uniform  vil)i'ations,  or 
any  series  of  sucii  tones,  could,  however,  be  reproduced  with  the 
greatest  accuracy. 

The  next  important  stej)   in   tin;  ]irogre.ss  of  invention   was 


252 


THE    SPEAKING    TKLEPHONE. 


obviously  the  discovery  of  some  means  whereby  the  proper 
amplitude  of  each  vibration,  or  succession  of  vibrations,  either 
sim2)le  or  compound,  could  ])0  directly  reproduced  by  means  of 
the  electric  current ;  and  when  this  was  once  done,  the  general 
problem  of  harmonii;  telegraphy  niiiy  be  said  to  have  been  solved. 
This  having  been  accomplished,  it  was  not  difficult  to  foresee 
that  two  important  practical  applications  might  bo  expected  to 
follow,  namely,  multij)lo  transmission,  and  vocal  transmission. 
I  believe  that  this  discovery  of  the  true  method  of  transmitting 
oom]iosite  vibrations  was  first  publicly  announced  in  the  Journal 
of  this  society,  1  in  a  paper  contributed  by  Mr.  Elisha  Gray,  it 
having  been  made  by  him  in  December,  1874.  It  consists  in 
causing  the  ett'ective  strength  of  the  electric  current,  by  which 
the  transmission  is  efTceted,  to  rise  and  fall  with  the  varying 
amplitude  of  the  vibrations  or  waves  whicli  are  to  be  reproduced. 
Nothing  could  be  more  simple  and  beautiful  in  a  th(>oretical 
point  of  view,  but  the  practical  exemplirication  of  the  method,  as 
is  usual  in  such  cases,  presented  considerable  difficulty. 

At  the  time  of  making  this  important  improvement,  Mr.  Gray 
had  already  been  engaged  for  more  than  a  year  in  endeavoring 
to  devi.se  a  ])ractical  means  of  transmitting  and  simultaneously 
reproducing  a  number  of  tones,  so  as  to  utilize  them  for  the 
jiurpose  of  multiple  tclegra})hy.  Let  us  briefly  glance  at  what 
he  liad  already  accomplished. 

It  was  observed  in  1837,  by  Dr.  Page.^  that  a  musical  sound 
was  produ('e(l  by  a  magnet,  between  the  poles  of  which  a  Hat 
.spiral  was  ])laced.  The  S(Mind  was  heard  whenever  contact  was 
made  or  broken  between  the  coil  and  the  batti'iy.  These  obser- 
vations were  confirmed  and  extended  by  De  la  Rive,  Wert- 
heiin*   and  many  others.     The  a])paratus  employed  by  these 

1  Gray,  Journal  of  Amfriean  Mectrieal  Society,  vol.  i.,  p.  la.  Tliis  uppnratiis  and 
its  inoilij  of  operation  will  bo  t'ouinl  iIcsitUh'iI  in  di'tail  in  (Iniy's  patcntK,  No.  1,874, 
of  .May  4,  Is^ii  (Gruat  Britain),  ami  lsil,:!4o,  of  .lannary  li'.,  1S77  (United  States^ 

"  Vugti  -American  Journal  oj  ,Scieiive  (first  series),  vol.  .\.\xii.,  p.  369;  ibid.,  vol. 
ixxiii.,  p.  3r.4. 

"  Do  la  Kive — "  Traits  li' Eleelricit^.thi'nrique  ef  a/)//?iyW'-'," 'T'-'itf'"*''  Translation, 
by  V.  ('.Walker,  vn],  i.,  ji.  30U; ;  alxo,  "  Kniglit'x  .VIoehanieal  Uiotionary,"  Arti- 
culating' ''  Telephone."' 

*  Ilii.l..  vol.  i.,  p.  ;!or. 


SOUNDS   PRODUCED   BY   MOLECULAR   CHANGES. 


253 


experimenters  ruiiy  Le  described  in  general  terms  as  an  electro- 
magnet with  a  self-interrupting  break-piece  attached  to  its  arnia. 
tnre,  and  another  magnet  in  the  same  circuit  for  producing  the 
sounds.  The  sounds  proceed  from  the  core  of  the  magnet  itself, 
and  arc  caused  by  the  molecular  change  which  takes  place  in 
the  iron  at  the  moment  of  magnetization  or  demagnetization. 
When  the  current  is  interrupted  a  sufficient  number  of  times  jjcr 
second,  the  successive  sounds  prod.uce  ujion  the  ear  the  effect  of 
a  musical  note.  The  method  by  whicii  (Iray  at  first  sought  to 
accomplish  the  desired  result  of  multiple  transmission  was  by 
arranging  two  or  more  self-interrupting  magnets,  adjusted  to 
different  rates  of  vibration,  so  as  to  close  the  circuit  of  the  same 
line  at  the  sending  station,  wliile  at  the  receiving  sliition  all  thi^ 
currents  passed  through  a  series  of  electro-magnets,  equal  in 
number  to  the  transmitters,  and  having  armatures  severally 
adjusted  to  their  respective  rates  of  vibration.  As  Mr.  (iray  has 
already  descrilied  this  apparatus  at  lengtli  in  a  preceding  numljer 
of  the  Journal,  1  I  need  not  enter  into  further  particulars  con- 
cerning its  construction  and  arrangement,  but  will  in  a  few 
words  jioiut  out  the  reason  why  it  failed  to  answer  its  intended 
purpose,  e.\ce2)t  to  a  very  limited  extent  Suppose  we  have  two 
self-interrupting  transmitters,  one  of  which,  a,  makes  six  vibra- 
tions in  the  same  time  that  the  other  one,  b,  maiccs  five.  If  we 
now  set  them  in  op  ration,  first  one  and  th(Mi  the  other,  and 
record  the  pulsations  on  chemical  ]}aper  at  the  receiving  station, 
we  should  obtain  the  results  sliown  in  fig.  121  atrt  and  b.  But  if 
both  are  set  in  operation  simultaneously,  wo  get  tlie  result  sliown 
in  the  third  line  of  the  figure,  at  c.  Now,  it  is  obviously  (piitc 
possible,  by  ins'.iriug  a  proper  relation  between  the  times  of 
vibration  of  two  or  even  more  transmitters,  to  avoiil  any  material 
interference  bctwi^en  the  different  sets  of  pvdsations,  but  a  limit 
is  very  quickly  reached,  because,  as  you  will  readily  perceive, 


'  Gray — Tnurnnl  .imiriran  fClecfrirdl  finrittij,  vol.  i,  pp.  5,  li.  For  detiiils  iiiul 
fiirtliiT  lU'scriptiou  srn  spoi'itiwitions  oC  Gniy'.s  ]mtiMits,  viz.,  'J,ii4ii,  of  .Inly  'JH,  l'*7t, 
uiiil  V~\,  ot'Mari'li  lii,  InT.')  ((Iroiit  Hritaiu) ;  also  No.  li!ii,iMt.-),  ot' July  'JT,  l^T.')  (trnited 
StuteH) ;  also,  "Knight's  Mechanioal  Dictionary, "'  .\rtii.'iiliitin)^  "Telephone." 


254 


THE   SI'KAKlX<i    TKI.EI'HOXE. 


any  considerable  number  of  tranpmitterfj,  acting  in  tliis  manner 
to  open  anil  close  tlic  same  circuit,  would  produce  a  continuous 
current,  and  no  analysis  of  the  separate  sets  of  vibrations  at  the 
receiving  station  would  be  jiossible. 

I  will  now  ])roceed  to  describe  in  general  terms  the  nature  of 
the  imjinjvemcnt  by  means  of  wliich  Mr.  Gray  was  enabled  to 
transmit  an  indefinite  nuuil)er  of  different  series  of  vibrations, 
without  destroying  their  individuality.  The  details  of  liis  sys- 
tem, and  the  particuhu-  application  of  it  to  nudtiplc  telegraphy, 
having  been  already  made  known  in  a  jircceding  number  of  the 
Journal,*  I  sball  not  attempt  to  enter  into  thcni  at  any  length. 

The  strength  of  current  in  any  circuit  may  be  varied  in  two 
ways :  by  employing  a  constant  electromotive  force,  and  varying 


Fig.  121. 

the  resistance  of  the  circuit,  or  el.se  by  varying  the  electromotive 
force,  and  allowing  the  resistance  to  remain  constant  Gray 
employed  the  latter  process  in  his  method  of  multiple  telegraphy. 
Each  series  of  vibrations  at  the  transmitting  station,  when  added 
to  the  existing  ones  by  the  depression  of  its  proj)er  key,  carried 
with  it  its  own  section  of  battery,  and.  tluM-cforc,  its  electromotive 
force  was  superposed  upon  that  already  in  the  circuit.  The 
effect  of  this  was  to  produce  a  resultant  current  of  varying 
strength,  which  would  be  properly  represented  by  a  curve  ident- 
ical with  that  representing  the  resultant  of  the  scvci-al  sets  of 
simple  Vibrations  at  the  sending  station.  The  analysis  of  the 
composite  vibrations  at  the  receiving  station  was  effected  bv  a 


•  Gray — Journal  Amerian  fJleitriial  Soi'iety,  vol.  1,  jip.  1.3  et  seq.  ;  iilso  nee  imtent.'i 
of  Grt-iit  Britain  and  United  Stuti;s,  roturrcd  to  in  note  2, 


IIEr-MirOLTZ  S   ANALYSIS   OF   VOCAL   SOUNDS. 


255 


scrios  of  olcctro-magnots,  tlio  several  armatures  of  wliich  were 
l)ars  or  plates  adjusted  to  a  certain  rate  of  vil>ration,  the  normal 
rate  of  each  armature  bar  dillering  from  that  of  the  other.  P^ach 
arniatiu'e  bar  will  i-espoiid  to  its  corresponding  set  of  vibrations 
on!}-,  and  it  makes  no  difl'ereiiee  wiiatever  whetiier  these  vibra- 
tions are  transmitted  alone,  or  \vh(>tlu'r  they  form  a  constituent 
part  of  a  compdsite  series  of  vibrations.  Eacli  set  (jf  vibrations 
is  broken  up  into  dots  and  dashes  by  the  action  of  a  key,  just  as 
if  it  was  an  ordinary  continuous  current.  But  as  a  matter  of 
fact,  the  main  circuit  is  never  broken,  although  the  stnuigth  of 
the  current  is  constantly  varied.  The  manner  in  which  these 
armatures  are  thrown  into  vibration  by  tlie  properly  timed 
impulses  of  the  electric  ciuTcnt  acting  upim  the  electro-magnet 
is,  as  you  will  readily  jierceive,  strictly  analogous  to  that  of  the 
swing,  which  can  oidy  be  set  in  action  liy  properly  timed 
impulses;  or  that  of  tiie  tuning  fork,  sot  in  vil)ration  by  the  tiny 
blows  of  the  little  atmospheric  waves,  in  the  manner  which  has 
already  been  e.x plained. 

Tlie  re|)roduction  of  articulate  vocal  soumls  at  a  distance. 
<lcpcnds  upon  ])recisely  the  same  fundamental  principle  as 
multiple  harmonic  transmission,  namely,  the  transmission  of 
composite  vibrations.  This  will  become  evident  fi'om  a  consid- 
eration of  the  character  of  articulate  sound.s,  such  as  tho.se  of 
the  human  voice.  The  analysis  of  vocal  sounds  was  first 
accomplished  by  Ilelmholtz.  ^  It  would  occupy  too  much  space 
to  detail  the  experiments  by  which  he  .succeeded  in  establish- 
ing the  fact  that  the  different  vowel  sounds  are  produced  by 
the  presence  of  a  fundamental  note,  mingled  with  higher  har- 
monics in  various  jjrojjortion.s,  a  harmonic  tone  being  a  weak 
or  jiartial  tone,  caused  by  a  rate  of  vibration  twice,  three  times, 
four  times,  and  .so  on,  greater  than  that  of  the  fundamental. 
The  several  vowels,  tiierefori>,  belong  to  the  class  of  sustained 
tones  which  can  be  used  in  nnisic,  while  the  character  of  conso- 
luints  mainly  depends  upon  brief  and  transient  noises.      The 


1  lleliiilmltz     .PiV  I.fhre.  von  ilem  Tnnempjinduntjtn  (Ellis"  Tr;iiislation\  Clmp.  IlL 


256 


THE   SPEAKING   TELEPHONE. 


pro])lem  in  this  onso  wiis  to  rcproflnco  at  tlio  reooivinp;  station 
prei;iscly  the  same  vibrations  in  the  atmosphere  as  tliose  pro- 
duced by  the  voiee  of  the  speaker  at  the  transmitting  station. 
We  have  seen  why  Reiss  was  unable  to  accomplish  this.  Let  us 
see  wherein  later  inventcjrs  and  discoverers  have  been  more 
fortunate. 

Some  time  prior  to  February,  1870,  Gray  conceived  tlie  idea 
of  attaching  to  a  stretched  membrane,  such  as  that  used  by 
Rciss,  a  resistance  aiii)aratus,  wl I i  should  ])e  placed  in  a  con- 
stant circuit,  and  caused  to  vary  with  tlie  vibratit)ns  of  the  mem- 
brane in  response  to  the  sonorous  waves  travi'rsing  the  atmo- 
sphere and  impinging  upon  it  Of  course,  if  this  could  bctlone, 
it  would  bo  easy  to  attach  an  electro-magnet  with  an  armature 
formed  of  a  circular  i)latc,  which  would  respond  to  vil)rations 
of  every  character,  and  thus  reconvert  the  waves  of  electricity 
into  aerial  sound  waves.  A  caveat,  describing  this  invention, 
was  fded  by  Gray  in  February,  1876,  and  himself  and  others 
have  since  been  engaged  in  perfecting  and  elaborating  it,  with 
a  very  satisfactory  degree  of  practical  success.  ^ 

We  will  now  turn  to  the  labors  of  another  inventor  in  the 
same  field,  Mr.  Alexander  Graham  Bell.  Like  Gray,  he  had 
been  for  some  time  at  w^ork  upon  the  problem  of  multiple  tele- 
gi'aphic  transmission  by  means  of  harmonic  vibrations,  and  when 
we  consider  that  each  of  them  appears  to  have  been,  at  least  as 
late  as  October,  1874,  in  entire  ignorance  of  the  labors  of  the 
other,  the  singular  coincidence  in  the  results  which  they  finally 
attained  was  not  a  little  remarkable.     Gi'ay  had  approached  the 


•  Since  the  tibovo  wiin  written,  Mr.  Tliornii.s  A.  Edison,  of  Menlo  Park,  New 
Jersey,  i.s  said  to  have  obtained  very  satisfiietory  results  with  a  telepliono  eon- 
strueted  upon  tlie  general  plan  set  forth  in  Gray's  eaveat,  i.  c,  a  variable  resistance 
controlled  by  the  vibrations  of  a  diaphragm.  Edison  made  the  discovery  that 
plumbago  possessed  the  curious  property  of  altering  its  electrical  resistance  in  pro- 
portion to  the  pressure  to  which  it  is  subjected,  and  availed  himself  of  this  dis- 
covery in  the  construction  of  his  telephone.  More  recently  the  snmo  c.vpcnnicnter 
is  said  to  have  obtained  still  better  results  by  the  use  of  carbon  in  the  form  ol'.lamp- 
black,  from  the  smoke  of  an  ordinary  liydrocarbon  lump,  compressed  into- u  eylm- 
dricul  button.    No  details  of  tluH  apporutus  Lave  yet  been  made  public. 


whicli 


HELLS  KXPRIUMENTS. 


257 


sul)jcct  from  tlic  stiiiul-poiiilof  ;ui  clcctriciati.  Tu'll,  on  tlio  other 
liiind,  was  a  pliysiolou^ist,  ami  so  a|i|'r(iarluMl  it,  from  tlio  o[)posito 
(lirectionj  if  I  may  iisd  liio  cxin-i'ssioii.  As  early  a^  18(17,  lie 
bocaino  iiitcre'stcd  in  tlio  rcsrarrlu'S  of  llclmliolt/,,  iM'caiiso  of 
their  beariii<^  upon  tlio  siibjci't  of  liis  professional  stiily,  voeal 
physiology,  or,  in  other  words,  the  mechanism  of  human  sj)eech. 
Ilia  earliest  experiments  appear  1o  have  been  made  in  Buslnn  in 
1872,  but  were  f^ubstantially  re[)etilions  of  those  idrcady  made 
by  irelmholtz.  In  November,  187;i,  ho  eomplete(l  an  ex|)eri- 
mental  instrument  witli  two  self-interrupting  transmitting  reeds, 
and  two  corresponding  receiving  reeds,  the  transmittcMS  being 
connected  in  multiple  are,  exactly  as  in  Gray's  first  metliocL 
For  reasons  whieli  have  alnnidybeen  given  in  speaking  of  Gi,.  's 
apparatus,  it  is  jiossible  to  transmit  two  separate  .series  of  vibra- 
tions without  material  intcrferenci;  in  ihi-  manner,  yet  a  limit  is 
very  soon  reached,  because  the  current  beeomi>s  practically  con- 
tinuous. Bell  continued  his  experiments  in  multiphi  trans- 
niissiuu  during  the  years  187-i:  and  1875,  but  it  does  not  ap])ear 
that  anything  of  practical  inip(U'taneo  in  that  direction  n'snlted 
from  them.  At  length  ho  .seems  to  have  turned  his  attention 
to  tho  development  of  the  speaking  telephone,  ami  in  the  spring 
of  1876  he  arrived  at  some  important  results.  In  a  communica- 
tion presented  to  tho  American  Academy  of  Arts  and  Sciences, 
May  10,  167(5,  and  publislied  in  tho  proceedings  of  the  soriety,^ 
Mr.  Bell  gives  a  .somewhat  detaih^d  account  of  his  rescjarches  in 
telegraphy  up  to  that  date.  I  quote  from  this  ])aper  the  follow- 
ing description  of  an  e\i)eriment  in  vocal  transmission,  prob.a,bly 
the  first  one  in  any  degree  successful,  which  a[i[icars  to  have 
been  made  by  liim  early  in  the  spring  of  187G,  and  is  of  great 
interest : 

"Two  single-pole  electro-magnets,  each  having  a  j'csistancii  of 
ten  ohms,  were  arranged  upon  a  circuit  with  a  battery  of  live 
carlion  elements.      The  total  resistance  of  the  circuit,  exclusive 


1  Si'o  paper  ri'ad  by  I'rof.  Bull  bef'oru  tlio  Sdc.  of  Tol.  Eiijjineors,  nn  abstmot  of 
wlik'li  may  lio  fuuiul  in  tlio  Tcl«jrapliic  Journal,  Vol.  V.,  ji.  i!T'i. 

'  Bell — I^ooeedings  of  American,  Academy  of  Arts  and  Sciences,  A'ol.  XII.,  p.  1. 


268 


TJIK  Sl'KAKINO  TKLEPIiONK. 


of  the  l)att(My,  was  alxnit  twcnt y-fivo  olimA  ]  )nini-lica(l.'^  of  jrold- 
bcatei's'  t^kiii,  seven  ct'iitiineliv.s  in  diaiiictcM",  -wcro  ])lace(l  in  front 
of  earh  I'leelro-nKignet,  and  a  circnlar  ]iieco  of  cl()ck-siiriii;.r,  ono 
centinietro  in  diameter,  was  glnecl  to  tlio  middle  of  cadi  mem- 
brane. Ti:o  telejiliones,  t«)  coiistrneted,  wcro  placed  in  different 
rooms.  One  was  retained  in  the  cxp(>rimental  room  ami  the 
other  takf-n  to  the  basement  of  an  adjoining  honso.  Upon  .sing- 
ing into  the  telej)honc,  the  tonesof  the  voice  wcro  reprodnced  by 
the  in.<tfnmcnt  in  the  distant  room.  When  two  persons  King 
simultaneously  into  the  instrument,  two  notes  wcro  emitted  sim- 
ultaneously by  the  tcle})h(jne  in  the  other  lionso.  A  friend  was 
sent  into  the  adjoining  building  to  note  tho  effect  produced  by 
articulate  speech.  I  placed  the  mendjrano  of  tho  telephone  near 
my  mouth,  and  uttered  the  scnteneo:  'Do  ^'ou  understand  what 
I  pay?"  Presently  an  answer  was  leturncMl  through  the  instru- 
ment in  my  hand.  Articulate  words  proceeded  from  tho  cloek- 
spring  attached  to  tho  iuend)rane,  and  I  heard  tho  sentence: 
'  Yi's  ;  I  understand  you  perfectly.'  Tho  articulation  was  some- 
what iiuiillcd  and  indistinct,  although  in  this  case  it  was  intel- 
ligible. Familiar  ([notations  wcro  generally  understood  nhvv  a 
few  repetitions.  Tho  effects  were  not  sufTicicntly  distinct  to 
admit  of  sustained  conversation  through  tho  wire.  Indeed,  as  a 
general  r\dc,  the  articulation  was  unintelligible,  excepting  when 
familiar  sentences  were  employed.  Occasionally,  however,  a 
scnteneo  would  como  out  with  such  stai'tling  distinctness  as  to 
render  it  diilicult  to  l)eIievo  tho  speaker  was  not  close  at  hand."i 
There  is  reason  to  suppose  that  Bell  liad  formed  some  idea  of 
tliei)ossibilityof  this  result  as  early  as  1874,  although  its  practical 
exemplification  does  not  appear  to  have  taken  place  until  shortly 
before  tho  date  of  tho  ])a])er  from  which  tho  above  extract  is 
taken.  It  will  bo  obser\cd  that  liis  method  diff(>rs  fi'om  that  of 
Gray,  inasmuch  as  the  latter  varies  tlie  resistance  in  tho  circuit 
without  changing  the  cleetromotivo  force,  while  Bell  varied  tho 
electromotive  force,  the  resistance  remaining  constant,     Tho  bat- 


tl 
a( 
lh 

en 
tilt 


1  Ibid.,  Vul.  XII. 


!'• 


SiMi,  iiLsc),  Teleiirnpk  ,h>ufiial^  vi^I.  V,,  p.  '.'77. 


Al'I'I.lCATlo.V   Ol-  I'KHMANKXT  MAGNKT.S. 


259 


tcry  cniTcnt  f-'Tvod  no  dtlicr  purjiosc,  in  BcH's  cx|ieniiioiit,  tlian 
to  lu'i'iiiiuiciilly  iiii'.giu'ti/o  llio  .siil't  ii'iiii  cnics  oC  tlio  cleclni- 
magiu't,  wliilo  till!  niiigncto-ii  id  net  ivo  waves  wcro  superposed.  In 
Septcmlier,  1876,  Prof.  A.  J'].  Dolliear  sulwtitutod  ii,  jicrnianent 
steel  magnet  for  tlio  ehictro-maLriietic  arrang(>iiient  ]ii'eviously 
employed  hy  I'x'll,^  ami  tlio  instriiiiieiit  thus  improved  is  now 
going  into  very  extensive  us(\  Its  jirlieiihition,  wliilo  distinct,  is 
not  very  loud,  altliougU  sudiciently  {<o  iii  a  wc;!! -const meted 
instrument  to  admit  of  lengthy  sustained  cmiversalions,  without 
the  slightest  misunderstanding  or  iv[ietilion.  Of  course,  it  is  not 
to  bo  expected  that  tho  loudness  of  this  form  of  tele]  ihono  can  be 
increased  very  greatly  beyoml  its  present  volume,  for  wo  can  at 
best  only  get  from  it  the  mechanical  equivalent  of  tho  liuman 
voice,  deducting  the  loss  inse])aralile  from  its  conversion,  first 
into  mccliauieal  motion,  then  into  electricity,  then  into  magnet- 
ism, and,  fmally,  back  iigaiii  into  motion.  Tho  most  striking 
results  are  to  be  loolo'il  for  in  the  direction  first  pointed  out  by 
!Mr.  Gray,  for  the  reason  that,  if  an  elTectual  method  of  con- 
trolling the  resistance  of  tlie  circuit  by  means  of  a  vibrating  dia- 
phragm can  bo  discovered,  the  source  of  power,  wliieh  in  this 
case  is  the  battery,  may  be  augincMited  to  any  recpiircd  extent. 
It  is  not  to  1)0  denied  that  the  problem  thus  presented  is  one  of 
exceeding  mechanical  difTicidty ;  but  there  is  no  reason  to  sup- 
])oso  that  it  may  not  bo  successfully  solved.  It  is  to  the  devehjp- 
meiit  of  this  variety  of  tho  speaking  tclophone,  rather  than  to 
that  of  tho  magneto-instrument,  that  inventors  will  find  it  most 
advantageous  to  turn  their  attention,  for  I  hazard  little  in  saying 
that  the  latter  has  already  reached  such  a  surprising  degreo  of 
elheicMicy  as  to  leave  comparatively  little  more  to  be  done  within 
tho  neccirsary  limitations  which  have  been  pointed  out 


Do]lK-ar— "  Tlif  Tdciilioiii.',"  ji.  110.     (Soo  iilso  profiico  of  huiuo  work.) 


CIIAPTKIi  A'lir. 


DOLBEAli's  TELEPIIOXIU   KESEAUCHES.  * 

Dl'kin'G  tlie  year  1854,  while  at  work  in  Alien  &  Tliiirbcr's 
pistol  factory,  in  Worcester,  Massachusetts,  I  l)e;j'an  to  make  ex- 
periments in  cleclrieily  and  maifnetism.  I  intrixluceil  at  that 
time  the  use  of  a  ^Jcrmanent  magnet  to  pick  up  the  small  parts 
of  the  looks  of  pistols  from  the  cases.  This  liad  previously  been 
done  by  the  enn)loyes  with  their  fingers,  which  were  often  made 
sore  by  the  nails  beint;  worn  olf  too  short.  ^I'lie  magnet  was 
adopted  by  those  having  that  kind  of  work. 

I  also  tried  to  make  a  porpetmd  motion  machine,  which  should 
derive  its  ]iower  from  ])crmanent  magnets.  I  also  constructed 
a  trough  battery  of  six  cells,  with  which  I  tried  many  experi- 
ments. 

1855.- — During  this  year  T  made  a  magneto-electric  machine, 
of  the  common  pattern.  Was  ri'iMpicntly  with  flcnrv  ^f.  Paine, 
wlio  was  then  trying  to  construct  a  successful  electromotor. 

1859. — ^[ade  another  magneto-electric  marhine.  Also  in- 
vented a  steam  whistle,  which  was  designed  to  ])lay  .any  tune. 
This  was  while  employed  in  Mason's  loc(;motive  works,  at  '^Paun- 
ton,  ^fassachusetts. 

1861. — Invented  and  constructed  a  gyroscope  to  rim  by  electro- 
magnetism,  (tonsisting  of  a  small  electro-magnet  revolving  be- 
tween the  poles  of  a  ])erinancnt  magnet,  sha[)e(l  like  the  letter  C. 

18G4.— Made  f<u-  the  Ohio  Wesleyan  C  liege,  at  Delaware,  O., 
a  laige  compound  permanent  magnet:  also  an  electro-magnet  for 
lecture  purposes.  I  invented  a  inagneto-clcclric!  telegraph,  in 
which  the  current  of  electricity  was  generated  by  the  action  of  a 
permanent  magn(>t  when  thrust  into  or  withdrawn  from  a  hollow 
bo!)bin.     This  was  di'signeil  to  move  a  needle.    Also  [)i\)posed  to 


1  Alislr.'ii't  fruiii   "  Ufsc'iirulics  in  Tclcplioiiy,"  liy  I'rot'cssor  A.  E.  Bolbeiir,  nf 
TulU  CoUujje. 


]>OI.BEAKS  TKLErilONlO   KErfKAHClIES. 


281 


have  a  like  instrument  at  the  receiving  station,  whieh  I  pupposed 
would  duplicate  tlic  movements  of  the  lirst  instrument.  The 
receiving  magnet  was  to  be  furnished  wilU  a  ])en,  and  thus  regis- 
ter the  movements  of  the  transmitting  one.  I  saw  that  the  move- 
ments of  the  sc(!ond  would  of  necessity  be  precisely  like  those  of 
the  first,  but  did  not  at  that  time  know  that  the  movement  of  the 
second  would  be  so  feeble  as  it  actually  is.  I  triced  to  interest  a 
number  of  persons  in  this  invention,  but  did  not  succeed.  As  I 
had  no  mcians,  and  was  working  my  way  through  college,  T  was 
compelled  to  abandon  the  projcict.  It  will  be  seen  that  the  ])rin- 
ciple  of  the  present  S])caking  telephone  is  es.scnt!ally  involved  in 
this  invention  of  1864. 

18G7. — Invented  u  gyroscope  to  run  by  electro-magnetism,  and 
which  demonstrates  the  rotation  of  the  earth.  This  was  whih;  I 
was  a  student  in  Michigan  University.  This  inacliine,  con- 
strucLcd  by  Ritcliie,  was  exhibited  at  the  Centennial  Exhibition. 

18()8. — Conducted  a  series  of  experiments  to  determine  the 
quantity  of  matter  transfcnvd  by  the  ek'^tric  spark.  The  ])]iu\ 
carried  out  was  as  follows  :  One  thou.sand  inch  sparks  from  an 
electrical  machine  wi-re  rect-ivcd  into  chemically  pure  hydro- 
chloric acid  from  a  ball  of  coj)pcr.  Tlu>  liquid  was  made  blue 
by  the  addition  of  ammonia,  and  thencompared  with  a  standard 
solution  which  was  reiluced  until  the  colnrs  of  the  two  were 
juilged  to  be  alike.  That  gave  ajiiirDximatcly  tlit;  transferred 
co]i})cr  for  that  numlx'r  of  sparks.  The  same  jilan  was  tried 
with  iron,  silver,  l(>ad  ami  some  other  substances,  using,  of  course, 
dilTercnt  reagents  with  ciicl!. ' 

1870. — Discovered  that  the  so-called  magnetic  ])hantoiu  was 
permanently  magnetic;  that  it  would  j<lace  itself  in  the  magnetic 
meridian,  and  in  all  respects  couqiort  itself  like  a  magnet. 

1871  and  1872. — ^fade  quantitative  measurements  of  the 
elongation  dfan  ii'nn  I'od  when  niagn('ti/e(l. 

1)\'  lixiiig  a  small  mirrnr  upon  the  hmg  arm  of 


1  A  note  of  ;  ju'su  oxpcriiiu'iits  wiiH  published  in  tlio  supplemunt  to  the  Chemical 

AV'M'S,  ill  till.'   M  lllll;r  111   iMl''-',). 


262 


THE   SI'EAKI\(}   TEI.EI'IIOXE. 


!i  Icvor  whilo  tlic  bar  acted  upon  the  short  ar;n.  A  1)onm  of 
light  was  ])r()jc'ctctl  upou  the  luirrur,  aitil  rellciMed  to  a  distance 
()[  lil'ty  feet.  The  angle  vi  its  disphieeinent  tlieu  admitted  of 
convenient  measurement.  Ki'iieated  experiments  ]iro\ed  that 
the  result  of  the  magnetization  of  an  iron  rod  was  an  average 
elongation  of  tj-j,' ,TiT  P'"'*'  '^^  ^^^  length. 

I  tried  to  cause  a  line  ratchet-wheel  to  revolve  by  a  recipro- 
cating motion  derived  from  this  slight  molecular  movement, 
making  ami  breaking  the  eironit  with  an  interrupter. 

1872. — ^^adc  some  veiy  large  forks,  capable  of  vibrating 
strings  twenty  feet  in  length,  fi>r  class  (h.'monstration. 

1873. — Made  some  large  tuning  forks  for  proj\'cting  sound- 
curves  u]ion  a  screen;  also  discovered  a  method  of  very  mueh 
amplifying  thesi!  viliratioiis.^  A  ])air  of  these  forks  was  ex- 
hibited at  the  Philadelphia  Exposition.  At  the  same  time  in- 
\ented  an  attachment  to  the  whirling-table,  for  accomplishing 
the  same  thing.2 

Discovered  convertihility  of  sound-vibrations  into  electricity. 
Using  a  tuning  fork  in  eonneetion  with  a  thermo-[iile  and  gal- 
vauometei',  1  noticed  that  when  tlie  fork  vil>rated  the  needle  wa.s 
deilected.  Further  observeu  tlie  ed'ect  of  a  vibrating  tuning  fork, 
which  was  also  a  ma;^iiet.  u|)ou  the  current  from  a  tlierm()-])ile. 

At  the  ]'ortland  meeting  of  the  American  Association,  in 
1873,  read  a  short  ])a|ier  in  regard  to  tiie  lirst  of  these  experi- 
ments, wiiich  1  thought  was  new;  but  said  notliing  about  the. 
second,  as  1  cousidci'cil  it  was  only  a  ])arlieular  easi;  of  magneto- 
curr 'uts,  which  wen-  well  known.  JN'everthelcss,  it  was  pre- 
cisely the  sanu!  thing  as  tlii'  uiidulafory  current  which  I'roiessur 
Bell  claims  to  h;ivc  invented  or  discovered. 

While  engaged  in  making  a  manometrie  flame  capsule,  T  in- 
vented the  o|ieidosco[ie.  •' 

1  also  ])roved  that  the;  shee't  of  air  issuing  from  a  sounding 


1  Sci'  .Intininl  (if  h'riDiliiii  fiin/itutf,  1^"'!. 

'  See  prncri-ililltrs  iif  .Vnic-ririlll  AsMii-illtioU,  l-ST'!. 

"  t>uo  Joitrual  of  Fraii,klin  /lutUiUe,  liIU. 


Ai'i'i'iidix  I. 


DOLBKAK  S   MAGNETO-ELECTRIC   TELEPHONE. 


263 


1 


orpran-pipo  vibrates  like  ;i  reed.  This  was  done  by  filling  nn 
oruaii  licllnws  with  smoke,  and  examining  it  through  a  slrobo- 
.<e()[iic  iHsk  while  escaping  from  the  pipe. 

1876. — Commenced  my  investigation  and  experiments  in 
tclepliimy,  using  at  first  a  llelmlioltz  interrupter  and  electro- 
magnets. Among  many  experiments  in  trunsmitting  s])eech  I 
tried  that  of  a  eoni<,'al  point  of  iron  fastened  to  the  middle 
of  an  npeido.seope  mcmljrani',  the  point  being  attaclunl  to  a 
fine  wire  in  such  a  manner  as  not  to  interfere;  with  its  freedom  of 
movement.  This  poiuu  dipped  into  a  mercury  cup,  and  the  idea 
was,  tliat  inasmuch  as  the  point  was  conical,  when  it  was  made  to 
ailvancc!  into  tlu"  mercury  it  would  pi'cscnt  a  notably  larger  sur- 
face, and  thus  lessen  tlie  resistance  of  an  electric  circuit  of  which 
it  formetl  a  part,  A  current  of  electricity  passeil  through  this 
aiTangemeut  and  an  electro-magnet  caused  the  latter  to  sound 
loudly  at  times,  l)ut  it  was  found  that  the  mercury  bounded 
away  from  the  [loint  when  tiio  latter  was  made  to  vibrate  rapidly, 
and  so  the  plan  was  aV)andoneil. 

Proposed  to  make  a  telephone  with  a  ])ermanent  magnet 
having  a  coil  about  oiir  pole  anil  a  piece  of  wire  fixed  to  an 
opeidoscopo  mcm!)rane,  to  be  vibrated  ^  '  tlie  voice  in  front  of 
this  ]iol(\  I  us(hI  thin  rul)ber  for  the  mend)rane,  and  was 
trouhlcd  to  keep  the  iron  from  clinging  to  the  magnet  when 
hrought  near  il. 

Tried  jiaper  diaphragm  with  iron  on  it,  but  did  not  have  sufll- 
cient  leisure  to  be  able  to  accomplish  my  oljject.  Meanwhile 
I  had.  while  singing  atrainst  a  .sheet  of  ]iaper  held  in  both  hands, 
fell  the  fiirce  of  the  souiid  \'il>rations  ujion  tin;  paper,  and  con- 
eluded  to  construct  the  telephone  vilirating  armaturi>  entirt'ly  of 
iron,  in  the  form  of  a  comjilete  plate  fastened  at  the  edges, 
insti'ad  of  I  icing  attached  to  a  membrane  as  before. 

1  mi'asui'cd  the  distance  through  whii'li  I  could  get  a  signal 
with  such  a  (tui'rent.  J  siu'ceeded  in  doing  so  through  a  n'sist- 
anee  of  fifteen  thousand  ohms, 

J  now  thought  of  obtaining  a  ])atent  upon  the  sjieaking  tele- 
phone with  iicnauncnt  magnets,  and  began  constructing  suitable 


264 


THE   SPEAKING   TELEPHONE. 


instruments  to  servo  as  ;i  ]iatpnt  model,  but  before  these  instru- 
ments were  eompictcil,  I  was  inlormeil  that  Professor  A.  Graham 
Bell  hail  declared  tliat  ho  liad  secured  a  patent  up(ju  the  same 
thing  two  or  three  years  l)efore. 

On  tlie  12th  of  Fcliniarv.  1877,  Professor  Bell  gave  a  lecture 
and  exhibition,  at  Salem,  Mass.  AVithiii  a  day  or  two  I  called 
upon  him  to  see  liis  fi.\tures.  lie  was  not  in,  but  his  assistant,  Mr. 
Watson,  showed  them  to  me.  They  were  substantially  like  mine. 
I  invited  Messrs.  Watson  and  Bell  to  come  to  College  Ilill  and 
sec  my  apparatu.s. 


Fi'j.  122. 


Fl(j.  123. 


Mr.  Watson  said  I'rofe.ssor  Bell  wished  to  know  what  the 
resistance  of  the  human  body  was,  and  asked  if  I  could  measure 
it.  I  promised  to  do  so,  and  in  a  few  days  sent  him  the  meas- 
urement of  the  resistance  of  the  bodies  of  about  twelve  students, 
for  whiih  !  re('(>ived  a  letter  of  thank.s. 

About  the  first  of  ^larch.  lo77,  1  chanced  to  see  tlu?  ollicial 
gazette  of  the  I'atcnt  Ollice,  containing  J'rofessor  B'll's  ]iatent 
of  January  30th.  I.s77,  and  found  that  I  had  been  deceived  in 
regard  to  his  having  ]iatented  tlie  application  of  permanent  mag- 
n(!ts  to  tlie  telephone  prcsioiis  to  my  iiiventimi.  and  acenrdiunlv 
went  to  con.sult  ;i  lawy^'r  about  it.  I  was  considerably  dis- 
couraged on  aci'ount  of  his  statement  of  the  ])robable  cost  of 
an  attempt  to  secure  my  ritzht.-:.  1  trifid  to  interest  several  ]ier- 
sons  in  mvcase,  but  without  success. 


DOLBEAR   ASSERTS   HIS  RIGUTP 


2r,5 


About  tlie  lirst  of  ^May  Profossoi'  IJell  lectured  in  Boston,  and 
jmblicly  declared  himself  to  ])«  without  a  comiK'titor.  I  at  onco 
challenged  his  statement,  iiifor  .liiig  liim  what  I  had  done;  yet 
ho  (continued  to  riMterale  his  statement  in  all  his  subsequent 
lectures. 

In  July  he  wrote  to  me  that,  as  ho  was  <jo\w^  to  Kurnpe,  he 
would  like  to  have  from  me  a  statemi  nt  of  what  I  had  done  in 
te!e|ihon\-.  since  he  desired  to  i\n  justice  to  all.  I  met  him  at  the 
house  of  Gardiner  G.  Hubbard,   Ks(i.,  in  Cambridge,  and  gave 


Fig.  124. 


* 


hin\  the  pa  -tieidars  of  my  work.  IIi>  acknowledged  that  I  had 
•uvented  the  j'lephone  indepcnch-ntly  of  himself. 

In  1877,  I  was  enabled  to  make  further  investigation  into  the 
e  mlitions  necessary  for  the  telegraphic  transmission  of  speech, 
and  have  tl)e  following  di.-^coverics  and  inventions  to  report  as 
the  result  of  those  investigations: 

A  eu.shion  for  the  vibrating  diajihragm,  by  which  greater 
amplitude  of  viliration  is  ohtained.  with  increased  .sonorou.s 
etlects.  Telephones  maiie  in  this  way  have  l)een  heard  one 
hundr(>d  and  lifty  feet  away. 

The  uda])tation  of  the  common  string  telephone  (lovers'  tele- 


266 


TUK   Sl'KAKIXd   TKLKI'HONE. 


jri'apli)  to  a  Morse  souihV-M'  or  rclav,  liy  wliiHi  s|u>ecli  iiiiiy  be 
traiisniitlnl,  the  same  iustnimcnt  acting'  cither  a^  receiver  or 
traiisiiiitler. 

That  the  streiigtli  of  tlie  souml  is  much  more  dciieiulont  ii]»on 
the  strength  of  tlu'  magnets  unci  si/e  f)f  iho  [ilate  than  upuu  tlu; 
diameter  of  the  wire  and  immher  of  turns  upon  the  ])ol)hin. 
Some  of  the  loudest  tones  liave  been  obtained  witli  bobbins  eon- 
taiuiug  but  two  or  three  ohms  of  number  2b  wire. 


Foj.  125. 


Thar  c  .'^njtnnnd  inagu(>ts  are  mui'h  b"itrr  in  every  respect 
than  singe  magnets,  and  li'e  compound  L'  magnet  is  the  licsf  of 
all  forms  which  have  l)een  tried. 

The  tuning  fork  call. 

The  devil's  fiddle  call. 

Tlie  1)ell  call — falling  harmonic  bell. 

Tlie  paper  diajiiiragm.  with  elcctrd-magnet  armature.  Sec  fig. 
124. 

The  liattery  telephone,  in  winch  plates  of  t  ,vo  dUrcrcnt,  metals 


TlIK   ,Sl'KAKl.\(r   KLKl'Tlilil'irONK. 


267 


aro  pc'pnrntod  hv  a  iion-coTidnctnr  in  such  u  way  as  to  make  a 
shiillow  cell.  \Vlioii  ii  sDi.nd  is  iiia(](^  a.ira'mst  one  of  thesi',  as 
al  .1.  lig-.  125,  tliij  curriMit  i'-oiii  the  crll  is  Invil^cn  \\[)  into  waves 
lircciscly  like  tlic  iiKiveiiuiits  of  tlic  sound  waves,  and  speech 
is  rendered  remarkably  dis:inel  from  the  emi^loyment  of  such 
a  sounder. 

The  cleetroiihonc  or  moditieil  Reiss  telephone  (lig.  126).  In 
thisinslniment  a  i-ing<il  wood,  (u/,  has  a  plate  of  iron. /-,  screwed 
to  one  side  of  it.  the  jilate  l>ein<r  in  metallic  eoniu^'tion  with  a 
serew-cLip  leading  to  a  battery.     Upon  the  opposite  aide  ol  the 


Fig.  126. 


riuir  is  a  cross  arm  /»,  through  ^vhich  jiasses  a  .screw  s,  carrying  a 
point  wiiieli  niav  headjustcil  at  any  iccpiired  distance  Iroui  the 
plate  J).  This  screw  s  is  also  in  metallic  connection  with  the 
other  terminal  cnp. 

If  a  rather  weal<  hattcny  of  two  or  three  gravity  ci'lls  l)e 
jmt  in.  eiivuit  with  this,  together  with  any  form  of  receiving 
t(-lephon.',  anil  the  point  he  screwed  down  so  as  to  touch  the 
nl.'itc.  and  anv  kind  of  a  sound  lie  made  in  the  cavity  in  front  of 
the  iilate  p,  the  circuit  will  he  fuade,  ami  In'okiMi  the  nunihcr  of 
tunes  iicr  second  <lue  to  the  jiiicli  of  that  souml,  and  the  like 


268 


THE    SPKAKIXfi   TKLKPHONE. 


pitch  will  he  given  out  by  tlie  receiving  toleplionc ;  the  loudness 
of  tliis  soiniil  will  (lepeiKl  u]iiiii  the  ability  of  the  receiver  to 
respond  to  the  pulsations.  The  tones  will  he  (|uitc  loud  from  a 
Morse  sounder,  or  from  a  relay. 

If  the  point  be  drawn  ])ack,  so  as  not  to  touch  the  plate  at 
all,  and  a  dro])  of  water  be  inserted  between  the  ])oiut  and  the 
]>late,  and  talking  or  singing  be  resumed,  tlie  articulation  becomes 
remarkably  good,  though  the  sound  is  not  very  loud. 

Tf  a  strong  battery  of  iifty  cells,  or  more,  l)e  put  in  circuit, 
and  the  screw  be  turned  down  so  as  to  have  a  jiunping  spark 
between  the  point  and  the  plate,  the  viVirations  of  the  latter  intro- 
duce a  variable  resistance  in  the  air.  If  at  the  same  time  there 
is  a  strong  current,  the  result  will  be  very  loud  talking.  Indeed, 
it  Avil!  1)0  hjudcr  at  the  receiving  than  at  the  sending  station. 
This  has  been  used  over  the  lines  between  Boston  and  Kcw 
York,  and  between  Mdford,  New  Hampshire  and  Boston.  In 
each  case,  every  person  in  the  room  could  hear  the  talking  from 
the  other  end  of  the  line.  In  this  device  it  is  found  best  not  to 
use  a  very  sharp  point,  but  one  having  a  surface  like  a  sewing 
needle,  with  aljout  one  eighth  of  an  inch  broken  off  from  the 
point.  Such  a  one  gives  much  better  results  than  a  sharp  point, 
for  th(!  ol)\-ious  reason  that  a  greater  (piantity  of  electricity  can 
pass  from  such  a  surface  than  from  a  line  point 

Tf  electricity  of  high  tension,  like  that  from  ar  ordinary 
electrical  machine,  be  used  instead  of  the  current  from  a  battery, 
the  result  is  the  saine ;  talking  is  j'ossiblc,  the  articulation  is 
good,  but  the  tones  arc  not  so  loud. 

Large  plate  for  a  call. 

If  the  plate  be  made  a  foot  or  more  in  diameter,  but  mounted 
near  the  middle  concentrically,  the  magnets  and  bobbins  being 
the  same  as  usual  in  sixc  and  strength,  tlie  jilate  may  I)e  struck 
with  a  billet  of  wood,  or  other  material,  and  the  thump  will  be 
very  loud,  as  heard  from  an  oi'dinarv  tcle])lione;  in  fact,  loud 
enough  to  be  heard  fifty  feet  away.  It  is  also  good  as  a  receiver 
call. 


]>01iUKAU.S    I'JtdJKrnO.V   AI'I'AHATUS. 


269 


AX   ATTAHirMKNT   To    TIIK    WHIRMNCr    'I'AHI.K     FOR    PKi  > )  ECTING 

I.ISSAJOU'S  CrUVKS. 

^  The  costliness  of  the  u.sual  ainmratus  for  tlio  projection  of 
Lissajoii's  curves  lias  led  me  to  devise  a  method  for  a(!eom]iiish- 
inu-  tJie  same  results  in  a  comparatively  inexpeiisiv(!  way,  \vhi(;ii 
proves  in  other  ways  to  hesujterior  to  tln^  metliod  with  viln'ating 
f  <  )rks. 

It  consists  of  the  followinLC  attachment  to  tiie  whirliuLC  table: 


Fi'j.  127. 

Two  posts,  2^  <'""^  t>''  i'i"G  made  fast  to  tin'  frame  upon  the 
opposite  sides  of  the  inci'tiu  phile  a.  A  small  wooden  j>idley,  s. 
{[vx.  127)  about  an  inch  in  diameti^',  is  made  to  turn  upon  an 
axis  that  is  made  fast  in  tlu;  jiost^),  and  witii  such  adjustment  that 
the  pulley  rests  upMU  the  plate  <i  and  turns  liy  friction  on  that 
])late.  It  is  best  to  have  a  thin  india  rubber  ring  upon  the  fric- 
tion ptdley,  to  insure  it  from  slipjiing.  Above  the  ]iulley.  the 
mirror  in  is  so  mounted  as  to  swing  in  azimuth,  and  is  made 
to  do  this  bv  a  wire  fastened  to  it  at  its  hiiiire  and  bent  into  a 


I  By  A.  K,  Pollicar,  ol'Uctliiiiiy,  W.  Vii.     Frnni  tlip  Proofcdiiiifs  of  the  Aiiiirlcaa 
Associutiou  I'or  tlio  Adviiucuiuciit  ul'Sciuuce.     I'ortluiicl  luuetiiij,',  August,  157^3. 


270 


TIIK   Sl'K.\KIN(l   TKI.KIMIOXK. 


loo]>  ^,  ill  ils  lower  iMid,  wliicli  is  npposilc  tlii"  face  of  tlu!  pulley 
5  (lij;.  128).  Auotiicr  twist  ill  tlu;  win-  ;tl  ')  will  bn  iicciicd,  for 
:i  ]iin  wliicli  is  fast  in  tho  post  p.  Tiiis  will  make  a  lever  of 
the  wire  /,  with  \\u'.  fulcrum  at  o,  and  if  it  is  i)roporlv  fasteneii 
to  the  hiuj;jofif  the  uiirror,  will  cause  it  to  vibrate  in  a  hori;5oiital 
plane  when  tlie  phite  a  nn'olves. 

A  somewhat  similar  arranL^cmeiit  is  made  for  the  other  side, 
save  that  tin;  friction  pullev  s'  lias  it3  bearing  made  fast,  in  a 
separate  piece  c,  which  is  so  fasten(>d  to  the  end  of  a  loiit;  screw 
<',  that  till!  wliohi  lixtiire  can  l)e  mo\-ed  to  or  from  the  centre  of 
the  ]ilate  ct.  The  piece  c  is  fiirnisheil  with  two  j^fiiides,  which  keep 
it  steady  in  any  ])Ia(\e  where  it  is  )mt.  The  mirror  m  \a  made 
to  tilt  ill  a  perpendicular  })Umo  by  an  arrangement  <piito  similar 


M'j.  128. 

to  the  former  one,  save  tliat  the  wire  connection  ha.s  its  lower 
end  bent  into  a  horizontal  loop,  through  which  a  pin  in  the  face 
of  the  pulley  s'  is  thrust.  This  is  pra(;tically  an  eccentric,  and 
being  directly  fastened  to  the  hinge  of  the  mirror  iti\  give.s  to  it 
an  angular  tuotion  proportional  to  the  distance  of  the  pulley  face 
pin  from  the  centre.  The  mirrors  should  bo  not  less  than  two 
inches  square.  If  then  the  pin  is  an  eighth  of  an  inch  from  the 
centre  of  the  friction  pulleys,  they  will  have  ample  angular 
motion,  much  larger  than  can  ever  be  got  from  foi-ks. 

It  in  eviilent  that  if  the  two  friction  pulleys  have  equal  dia- 
meters, and  they  are  at  equal  distances  from  the  centre  of  the 
plate  a,  they  will  vibrate  in  unison  in  their  respective  planes. 


DoMiKAKS    I'lio.rKCTIOX    Ari'AUATI.'S. 


271 


Now  let  !i  l)c;iiii  <il'  \\'j:]]\  r,  iVnni  llic  iiortc  ImniiM-c,  fall  ii|Min  tlu; 
inii'i'or  ///.at,  such  an  aii^-'lcas  to  Ik;  I'cllccicil  lirst,  upon  tlit;  luirror 
7//'.  tlicncc  to  the  screen,  If  tin;  plato  a  is  now  revol\eil,  tin? 
I)i'ani  (if  liiilit  will  (Icscrilio  a  circle,  an  ellipse,  or  a  sti'ai,Liiit 
line,  eitlicr  uf  wliich  c,-in  lie  niailc  at  will  by  siiuplv  ailjusling 
the  crank  of  one  of  the;  mirrors  to  tlio  rc(piirc<l  an^lc.  'llnis, 
snppo.se  tlu!  mirror  m'  is  ti])peil  l)ack-  its  farthest  by  l)rin<_Mnjf  tlio 
pulley  pin  at  the  top,  as  inili<Mte(l  in  the  di-awin,!/,  at  the  same 
fiino  that  the  miri'or  m  is  at  its  maximum  anLrul.(r  (|e\iatioii. 
The  beam  of  li,L''lit  will  describe  ii  circle. 

If  it  moves  slowly,  the  jiath  ami  <lireetiou  of  the  inovinL-'bcam 
can  be  nicely  observt'd.  These  two  iidvant'ij^es  are  nut  to  bo 
had  with  forks;  for,  first,  it  is  accidental  if  tmi)  frets  ac-ircloor 
any  other  desired  resultant  fij^nires  from  forks  in  unison,  for  the 
obvious  rea.><on  that  llu;  ])hases  cannot  Ix!  regnlatcil :  ami  second, 
the  vibrations  of  the  forks  are  so  rapid  th.it  the  analysis  of  the 
motion  can  only  bi;  made  in  a  me(;hanico-mathematical  wav. 

By  moving  the  fixtures  on  the  left  side  towaril  the  centre  of 
the  plato  a,  the  ])ulley  s'  will  not  revolve  so  f;i>it.  Tf  moved 
half  wav,  it  will  make  one  revolution  while  the  other  makes 
two,  jind  the  vibrations  stand  in  the  ratio  1  :  2,  represented  by 
forks  in  octave.  Such  ratio  is  shown  np(jn  the  screen  by  a  form 
very  much  like  the  figui'c  8,  and  known  as  the  lemni.scate. 

Between  the.so  two  jilaces,  every  musical  ratio  in  the  octave 
can  be  got,  and  the  resultant  motion.^  ])rojected  in  their  proper 
curves.  More  than  that,  while  the  mirrors  are  both  vibrating,  any 
of  the  ratios  desinnl  can  be  moved  to  at  once  by  merely  turning 
the  thund)  screw  d,  which  is  wholly  impos.siblo  with  any  forks, 
which  reipi.ire  .-toppage  and  adjustment  of  lugs  for  each  different 
curve. 

Again,  if  the  i.  ::tnrG  c  is  moved  .still  farther  toward  the  centre 
than  half  \\  r.\  tie  curves  projectdl  will  be  those  belonging  to 
the  pc^'oml  ociave,  until  the  )iullcy  I't.'aches  three  foui'ths  of  the 
way,  when  the  ratio  will  be  1  : 4,  and  the  resultant  figure  will 
be  like  a  much  flattened  double  eight. 

If  one  would  show  the  phenomenon  of  beats,  it  will  be  ncces- 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


Y 


A 


{/ 


^  J^4i. 


V- 


u. 


^ 


s 


10 

I  I.I 

11.25 


lU 


1.8 


1.4    11.6 


Pm 


^^ 


^l^^   %''" 

"^/^i 


'/ 


photographic 

Sdences 

Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y.  145C0 

,716)  872-4503 


j9 


\ 


iV 


4!> 


272 


THE   SPEAKING  TELEPHONE. 


sary  to  have  tlie  mirror  m  and  its  attachment  so  adjusted  as  to 
have  it  vibrate  in  a  perpendicuUir  plane  like  m'.  This  can  be 
done  by  fixing  its  hinge  at  right  angles,  and  the  rest  the  same 
as  foi  mirror  m'.  The  reflected  beam  from  the  second  mirror 
may  be  received  upon  a  large  mirror  held  in  the  hands,  and 
thence  reflected  upon  the  wall  or  screen.  All  the  phenomena 
of  vibrations  that  can  be  shown  by  foi-ks  can  be  reproduced 
on  a  scale  that  is  not  approached  by  means  of  them,  by  any 
one  possessing  a  turning  table,  and  at  less  than  the  fifth  of  their 
cost 


ON   THE   CONVERTIBILITY   OF   SOUND    INTO   ELECTUICITY. 

^  I  have  found  by  experiment  that  if  a  vibrating  tuning  fork 
have  its  sti.'m  ajiplied  to  the  face  of  a  thermo-electric  ])ile  wliich 
is  in  circuit  with  a  delicate  galvanometer,  the  needle  will  be  dc- 
fiected,  showing  that  electricity  has  Ix'cn  develo})cd  in  the  pile. 
The  question  is  as  to  its  immediate  origin.  It  may  be  assorted 
that  the  vibrations  of  the  fork  arc  competent  to  develop  heat, 
which,  in  its  turn,  is  converted  inio  electricity,  so  that  its  appear- 
ance is  a  secondary  phenomenon.  To  this  explanation  counte- 
nance is  given  by  the  exjiei-iment  of  Professor  Henry,  who  found 
that  the  deadening  effect  of  a  rubber  cushion,  when  the  stem  of  a 
vibrating  fork  was:  put  upon  it,  was  due  to  the  fact  that  tluM-ibra- 
tions  were  converted  into  lieat.  But  the  vibrations  ai'o  not  no- 
ticeably deadened  in  the  former  case,  and  the  junction  of  the 
metals  is  subject  to  definite  and  measurable  vibrations. 

The  antecedent  to  the  production  of  electricity  is  the  contact, 
either  mediate  or  immediate,  of  substances,  wliieh  dilfer  ineompo- 
sition  or  in  condition,  and  if  electricity  is  a  mode  of  motion,  it 
ought  to  appear  whenever  .1  motion  may  be  set  up  at  such  point 
of  contact  as  mutually  to  disturb  the  molecules  of  the  differently 
constituted  matter.  That  the  vibrations  of  the  fork  are  compe- 
tent to  do  this  without  necessarily  giving  rise  to  the  phenomenon 

1  By  A.  E.  Dolbeur,  of  Botliiiiiy,  W.  \n.  From  tlio  I'rocccdiiijrs  of  tlio  Amuricau 
Associatiou  for  tho  Advaucomuiit  uf  Sc'iuuue.    I'ortluud  iiiuutiii);,  Aui;u.st,  \>i1'i. 


CONVEKTlBILIXy   OF   Soi'Nli   INTO   ELKCTRICITY. 


273 


of  heat,  may  fairly  l)c  inferred,  I  tliink ;  so  that,  a  priori,  one  should 
look  for  electric!  phenomena  from  such  a  >mbination  of  favorable 
conditions.  At  any  rate,  it  will  hardly  he  asserted  by  any  one 
that  because  tlu;  electricity  is  gi'iieratcd  in  the  thermo-pile  its  im- 
mediate cause  must  be  heat.  1  do  not  know  that  it  has  ever  been 
])rovcd  that  heat  motion  was  theoidy  kind  of  motion  that  was 
caj^able  of  direct  conversion  into  electricity  in.  the  so-called 
thcrmo-pair.  It  is  probal)le  that  the  more  general  statement  is 
true,  namely,  that  molecular  disturbance  at  the  junction  of  dis- 
similar metals  will  give  rise  to  electricity. 

We  know  that  the  niole<-ular  disturbance  called  heat  will  give 
rise  to  It,  and  it  is  not  improlcible  that  the  disturbance  caused  by 
a  regularly  vibrating  tuning  fork,  may  do  thesamo  thing  directly. 
My  exi)eriment  does  not  prove  that  such  is  the  case,  but  it  hints 
at  it,  and  I  olTcr  these  considerations  to  meet  the  objections  of 
some  who  take  it  for  granted  that  it  cannot  be  true  that  sound 
viVjrations  arc,  really  converted  into  electricity,  except  in  an  in- 
direct way.  This  is  ea[iable  of  verification,  I  do  not  doubt,  but 
I  have  not  had  time  to  apply  the  experimcntum  crucis,  as  the  idea 
did  not  occur  to  me  until  a  day  or  two  ago,  and  I  bring  it  to  the 
association  as  an  interesting  experiment,  whatever  its  ratioaale 
may  be. 


CHAPTER  IX. 


litPKOVEMEXTS  OK  CII.VXXIXG,    BLAKK   AND  OrHERS. 

In  the  winter  and  spring  of  1877  a  notable  series  of  experiments 
were  made  b v  a  few  soientilic  gentlemen  in  Providence,  R  I. ,  which 
resulted  in  making  tlie  teleplione  portal)le,  and  in  giving  to  it 
distinct  articulation.  ICvery  step  loading  to  these  important 
results  was  communicated  to  Prof.  B(>11,  and  the  principal  im- 
provements thus  originating,  especially  the  handle  instrument 
and  the  mouth-jiicco,  were  at  once  adopted  by  him,  and  form 
j)art  of  what  is  now  commonly  known  as  the  handle  telephone. 

In  March,  1877,  the  speaking  telephone,  in  its  most  practical 
form,  consisted  of  a  box  resembling  a  photographer's  camera,  with 
a  two  inch  tube  for  mouth-piece,  opening  into  a  cavernous  air 
chamber  in  front  of  a  plate  of  sheet  iron  about  4J  inches  in 
diameter.  Behind  this  plate  was  a  large  TJ  magnet,  with  a  soft 
iron  core  clamjied  to  each  pole,  surrounded  with  a  spool  of  fine 
insulated  wire.  These  instruments  were  unwieldy,  and  their 
articulation  defective,  for  three  reasons :  First,  the  mouth-piece 
did  not  converge  the  air  on  the  centre  of  the  plat-  and  the 
cavernous  air  chamber  produced  reverberation;  second,  the 
magnet  <lid  not  react  symmetrically  with  the  centre  of  the 
])late,  but  tlie  two  poles  or  con>s  of  the  U  magnet  reacted  with 
the  parts  of  the  plate  which  were  opposite  to  them  on  each  side 
of  the  centre;  third,  the  plate  was  too  large  and  heavy  to 
respond  perfectly  and  promptly  to  the  average  voice. 

Experiments,  eonuncncing  in  the  physical  laboratory  of  Brown 
University,  and  continued  several  months  by  Prof.  Eli  W.  Blake, 
Prof.  John  Peirce,  and  others,  culminated,  in  April,  in  tlie  con- 
struction, by  Dr.  William  F.  Channing,  of  tiui  iirst  portable 
telephone.  This  consisted  of  two  small  blocks  of  wciod  fastened 
to  each  other  at  right  angles — one  perforated  for  the  mouth-piece 
and  holding  a  ferrotype  plate,  2^  inches  in  diameter  ;  the  other 


IMPROVEMENTS   UV   PROVIDENCE    EXPERIMENTEHS. 


275 


sup])ortinff  a  c'nin])ouii(l  U  inagnet  (mado  of  two  three;  incli  toy 
inaguots)  witli  a  .single  soft  iron  core,  carrying  a  spool  of  iine  insu- 
lated wire,  clamped  to  one  of  its  ])oles  and  opposed  to  the  centre 
of  the  ferrotype  j)late.  The  other  ])olc  of  the  compound  magnet 
was  either  brought  in  contact  with  the  outer  edge  of  the  plate  or 
left  free. 

This  little  instrument,  weighing  about  twelve  ounces  and 
easily  held  in  tlic  hand,  especially  when  mounted  on  a  handle, 
talked  more  distinctly  than  the  large  in.strumcnts,  cvcmi  over 
long  circuits,  thougli  not  quite  so  loud.  It  was  followed  later 
in  April  by  a  telephone  made  by  Prof.  Peircc,  in  which  a  small 
(iompound  (J  magnet  was  enclosed  in  a  cubical  block  of  wood, 
on  the  top  of  wliieh  he  placed  for  the  finst  time  his  converging 
mouth-piece — an  acoustic  apparatus  which  deserves  .sjjccial  de- 
scription. 


Fig.  129. 

This  is  .shown  in  .section  in  fig.  129.  The  sound  waves  con- 
verge u[)on  the  centre  of  the  plate  through  the  aperture  a,  usually 
about  j'jj^  inch  diameter. 

The  sound  waves  also  spread  symmetrically  from  the  centre, 
and  act  upon  the  plate  through  the  very  flat  air  chamber  b  b. 
To  prevent  resonance  and  ensure  the  prompt  response  of  the 
plate,  this  air  chamber  is  u.sually  made  only  from  ^  to  j\  inch 
in  depth,  and  about  If  inches  in  diameter  when  a  ferrotype 
plate  (c  c)  is  used.  This  mouth-piece  made  distinct  and  natural 
the  previously  obscure  articulation  of  the  telephone. 

At  the  time  i'rof.  Peiree's  mouth-piece  was  made.  Prof.  Bell 
liad  arrived  at  the  disctovery  that  the  instruments  talked  better 
if  the  air  chamber,  usually  made  deeper  than  that  shown  in  fig. 
53,  was  stulTed  with  paper.  The  reason  will  be  sufficiently 
obvious  from  the  above. 


276 


TJIK   Sl'EAKING   TEI-Kl'HoyK. 


Prof.  Peirce'ri  npriglit  block  ^vas  followed  niitiirally  by  tlie 
"liamilc  teleplioiio,"  now  in  general  use,  whicli  was  made  l)y  Dr. 
Clianning early  in  ^[ay,  1877.  Figs.  1?,(^  and  131  slioi'.'-  both  a  sec- 
tional and  penspcctive  view  of  the  instrument.  In  this  a  small 
straight  magnet,  simple  or  compound,  carrying  a  single  soft  iron 
core  and  spool,  is  enclosed  in  a  light  and  elegant  handle,  and  the 


Mg.  130. 

ferrotyjie  plate  is  mounted  in  the  circular  head,  of  which  the 
moutli-piece  forms  part.  Tlie  design  and  .stylo  of  the  instrument 
is  due  to  Mr.  Edson  S.  Jones,  another  of  the  Providence  experi- 
menters. '  . 

After  a  competitive  test  with  the  box  telephones,  as  at  that 
time  made,  tlie  handle  telephone  was  adop.ed  and  sent  out  early 


fiy.  m. 

in  June  by  the  Telephone  Company ;  and  its  portability,  ele- 
gance and  superior  articulation  contributed  largely  to  the  ra])id 
diffusion  of  the  telephone  in  this  country  and  in  Europe  which 
immediately  followed. 

Prof.  Bell  was  familiar  with  the  preceding  Providence  experi- 
ments which  had  already  made  tlie  telephone   portable,  and 


m 
P 

hi 


In 

nil 

sh. 

cir 


lill'KOVEMENTS   liY   I'UOVIDEXCK   EXl'ElU.MENTEUri.        277 


which  suggested  tlic  liandle  form.  In  May,  shortly  after  the 
construction  of  tlie  handle  instrument  in  Providence,  and  before 
it  reached  Boston,  Prof.  Bell,  working  in  the  same  direction, 
had  put  a  U  magnet,  each  pole  armed  witli  a  core  and  a  spool, 
inside  of  a  handle.  The  instrument  was  too  cumbrous  and 
i  lelegant  f^r  adopjon,  as  well  as  defective  in  construetion. 
j'rof.  Bell's  desire  to  put  both  poles  of  the  magnet  to  visible 
use  was  especially  unfortunate  in  this  case,  as  tlie  smallness  of 
the  plates  in  the  portable  telepliones  makes  it  impossible  that 
the  two  poles  of  the?  TT  magnet  should  act  anywhere  near  the 
centre  of  the  plate.  Tlie  instrument  was  not  adopted,  and  it 
could  not  have  accomplished  for  the  diffusion  and  commercial 
success  of  the  telephone  what  was  done  by  the  original  handle 
instrument. 

Y"et,  with  no  other  basis  than  this  experiment.  Prof.  ]5ell. 
in  his  lecture  in  London,  before  the  Society  of  Telegraph  En- 
gineers {tice  page  7t)),  says  :  "  Two  or  three  (hiys  after  I  had  con- 
structed a  telephone  of  the  portable  form,  containing  the  magnet 
inside  the  handle.  Dr.  Channing  was  kind  enough  to  send  me  a 
pair  of  telephones  of  a  similar  pattern,  which  liad  l)een  invented 
i)y  the  Providence  exj)erimenters."  As  already  stated,  the  in- 
strument thus  referred  to  is  an  accurate  representation  of  tlie 
handle  telephone  of  Dr.  Channing  and  Mr.  Jones,  which  lias  had 
so  wide  a  career,  and  dill'(M-s  bi-oadly  in  typo  from  the  experi- 
mental instrument  of  I'rof.  Bell,  which  never  jm-ssed  into  nsc. 
Prof.  Bell,  in  the  above  extract,  not  only  claims  the  origination 
of  the  handle  telephone,  which  has  gone  round  the  world  and 
has  a  recognized  place  in  the  history  of  speaking  tck^phony,  but 
he  also  implies  that  he  gave  to  the  ti'lc]ilione  jmrtable  form, 
thus  ignoring  one  of  the  2)rincii)al  contributions  of  the  Provi- 
den  ■'!  cxpei'imenters. 

It  happencil  with  the  telephone  as  with  the  ]\[orse  telegraph. 
In  the  l)e<'inning  it  was  supposed  that  the  power  of  the  instru- 
ments was  proportioneil  to  their  size.  Later  experiments  have 
shown  in  V>oth  tliat  more  ilelicatc  instruments  are  tiie  most 
clleeti  ve. 


278 


TIIK    Sl'EAKINa    TKLKPHONE. 


It  will  1)0  ol)scrv('il  that  Professor  Bell  is  criticised  liorc,  not 
for  cl;iiiiiing  that  ho  had  made  a  straight  magnet  tck'phonc,  but 
for  claiming  this  in  comV)inatiou  with  the  handle,  and  iiguring 
tiiis  combination,  which  constitutes  the  well  known  handle  iu- 
strameiit,  as  his  own.  His  real  claim  is  to  the  independent 
experiment  of  jJUtting  a  U  magnet  in  a  handle,  subse(pient  to 
the  construction  of  the  genuine  handle  instrument  in  Providence. 

Another  ])i-aetical  result  obtained  in  Providence  as  early  as 
June,  was  tlie  glass  plate  tel(>plione  of  ]Ienry  W.  Vaughan, State 
assayer.  A  disk  <  t  soft  iron,  about  the  size  and  shape  of  a 
nickel  cent,  was  ccnientcd  with  shellac  to  the  centre  of  .a  very 
thin  glass  plate,  2^  inches  iu  diameter.  This,  with  Peircc's 
mouth- [liece  and  the  usual  magiu'ts,  gave  the  loudest  and  clear- 
est articulation  attained  at  that  or  at  a  later  tini(>,  and  may  be 
the  germ  of  important  improvements.  Mr.  Yaughan  also  nuide, 
before  the  tele]ilionc  had  been  soen  in  Fir.nce,  what  has  since 
been  described  as  the  midtiple  tLlephone  of  M.  Trouve.  In  this 
telephone,  plates  form  the  sides  and  ends  of  a  cubical  or  i)oly- 
hedral  chamber,  a  magnet  and  coil  being  behind  each  i^hite. 

Among  other  scientific  observations  with  the  telephone,  Prof. 
Pcirco  heard  the  auroral  Sfuind.s  early  in  the  summer  of  1877, 
and  Dr.  Chaiming  noticed  the  characteristic  telephonic  .sound  of 
lightning,  even  when  distant,  ])rcceding  the  visible  flash.  Prof.  E. 
W.  Blako  mailo  the  capitid  experiment,  im])erfectly  reported  in 
Prof.  Bell's  lecture,  of  substituting  a  soft  iron  bar  for  the  nuignet 
of  the  telephone.  Whenever  this  bar  was  turned  iu  the  direction 
of  the  di])]nng  needle,  the  telephone  would  talk  by  the  earth's 
magnetism;  but  when  swung  up  into  a  position  at  right  angles 
with  the  dipping  needle,  the  telephone  became  ])erfectly  silent 
Prof.  Blake  also  talked  with  a  friend  by  telephone  for  a  short 
distance,  using  the  parallel  rails  of  the  san\e  railroa<l  track  as 
conductors,  and  hearing  at  the  same  time,  by  induction,  the 
Morse  operating  from  the  telegraph  wires  overhead.  This  illus- 
trates the  apparent  indilfcrenco  of  the  telephone,  at  times,  to 
insulation.  Prof.  Blako  also  originated  the  responsive  tuning 
forks,  in  which  two  forks  of  the  same  musical  pitch  are  magnet- 


SII'HON   RECOUDElt  TELEPHONE. 


279 


izod  ;  n,  short  iron  cop',  stirrouiuU'd  witli  a  spool  of  wire,  is  sup- 
ported between  the  ]i 'les  or  proiiL'^s  <>!"  eiicli.  Tlir  wires  licing 
eonnected,  if  one.  tuniiii.'  fork  is  struck  tlie  otiifi-  responds  at  a 
distance. 

Tlie  iiiimes  of  Messi"s.  Jiouis  W.  Clarke  and  Charles  E.  Austin 
should  he  mentioned  among  tlie  corps  of  Providence  experi- 
menters as  contrihiitors  to  this  cha[)tiT  of  telephonii;  progi'css. 

1  With  the  ohjeet  of  stimulating  inqtiiry  into  the  means  of 
improving  the  telephone,  which  is  the  most  beautiful  adaptation 


Fig.  132. 
of  telegraphy  ever  made,  I  desire  to  draw  attention  t«i  a  few 
sim])le  methods  by  which  any  one  may  satisfy  himself  of  its 
])raeticahility  ;  for  no  one  having  witnessed  its  performance  can 
fail  to  sec  a  great  future  before  it 

The  recorder  of  Sir  W.  Thomson,  shown  ii\  fig.  132,  affords  a 
ready  means  of  speaking,  and  gives  out  such  clear  tones  as  to 
make  the  listener  at  first  involuntarily  look  behind  the  instru- 
ment for  the  speaker  (who  may  be  miles  away).     It  sulficcs  to 


1  Juliu  Gott.     Journal  Society  TeUgraph  Engineers.     No8.  XV.  und  XVI.    1S77. 


280 


THE   Sl'EAKING   TELKPIIOXE. 


take  a  tube  two  iiiclios  in  diameter,  and  stretch  over  one  end  a 
membrane  of  parcliment  or  tiiin  gutta  pcrelia  (tlie  latter  is  less 
allec'ted  by  the  breath,  the  former  becoming  somewhat  flaccid 
after  a  time).  To  the  centre  of  the  membrane  cement  a  straw, 
and  fix  the  tube  in  front  of  the  instrument,  about  six  inches 
from  the  movable  coil  li ;  cement  the  otlu-r  <,'nd  of  the  straw  to 
the  coil  at  the  point  where  the  silk  fibre  k  is  usually  fixed.  This 
is  all  that  is  necessary  for  both  speaking  and  receiving.  Six  or 
eight  cells  of  battery  connected  in  circuit  with  the  electro-mag- 
nets sullice.  A  pair  of  these  tubes  may  also  be  connected  in  a 
similar  nuinner  with  the  tongues  of  two  polarized  relays.  The 
tube  is  to  be  fixed  in  a  convenient  ])osition,  at  right  angles  to  the 
tongue,  and  the  free  end  of  the  straw  cemented  to  the  tongue, 
taking  care  that  the  latter  is  free  fmm  its  ordinary  contact 
points.  No  battery  is  required  for  sjjcaking  with  this  arrange- 
ment. 

Or  a  pair  of  these  speaking  tubes  may  be  connected  with  the 
ordinary  armatures  of  any  instrument  or  relay,  and  a  curi'ent 
kept  on  the  line.  The  armature  should,  however,  not  be  too 
heavy,  and  should  be  carefully  adjusted.  The  best  adjustment 
gives  the  loudest  sound.  In  sending,  be  c/ivful  that  the  arma- 
ture in  vibrating  does  not  touch  the  cores  ot  the  electro-magnet. 

A  plate  of  thin  iron,  such  as  is  used  for  stove  pipes,  fixed  to 
an  ujiright  board,  the  hitter  hollowed  out  on  the  side  on  which 
the  ])late  is  fastened,  and  a  hole  made  in  the  board  in  front  for 
inserting  ji  eonvenient  tube  for  speaking,  may  be  used  as  an 
armature,  and  a  pair  of  coils  placed  in  front  of  the  iron  plate 
through  which  a  current  from  a  battciy  is  flowing,  the  cores  to 
be  adjusted  as  close  as  possible;  to  the  plate;  this  answers  for 
.sending  and  rci'civing.  The  battery  need  not  be  strong;  if  it 
be  so,  the  armatures  have  to  be  removed  further  away  from  the 
coils.  On  a  short  line  the  resistance  of  tlie  coils,  with  a  suitable 
battery,  is  of  little  imj)ortance.  I  have  sjjoken  as  well  with  small 
coils  of  three  ohms  as  with  400  ohms. 

If  a  pair  of  coils  at  the  receiving  end  be  placed  on  a  violin, 
and  connected  to  the  line  on  which  there  is  a  permanent  current 


nEMAUKAHLE  TELEPnoXK*   TIIENOMENA. 


281 


nnd  a  scTnling  instrument  as  described,  singing  ar..'i  speaking  into 
the  tube  at  tiie  distant  end  can  be  heard  by  j)..  ,,.ifi;  tiic  ear  to 
the  violin.  The  elTcct  is  exalted  by  hiying  a  plate  of  iron  on 
the  poles  of  the  clectro-niagnet. 

By  th(;se  simple  means — and  tliey  are  selected  as  being  within 
the  reach  of  many — may  bi^  demonstrated  the  possibihty  of 
speaking  over  miles  of  telcgrapli  line.  The  sound  of  the  voice  in 
the  tube  is  not  that  of  a  whisper,  but  of  a  voi(!e  at  adi.stance; 
and  the  nearer  you  seem  to  bring  the  sound  the  better  your 
adjustment,  and  vice  vcixa 

I  have  s])oken  through  four  knots  of  buried  cal)le  without 
.sensible  tlimiuution  of  etl'eet. 

When  the  instruments  are  not  well  adjusted,  some  words  will 
come  clear  when  others  do  not ;  and  I  have  found  the  sentence, 
Arc  you  ready  ?  pronounced  deliberately,  intelligible  when 
others  were  not. 

The  object  to  be  sought  for  is  to  augment  the  strength  of  the 
variations  of  current  At  })re.sent  it  is  limited  by  the  power  of 
the  voice  to  move  an  armature  or  coil ;  and  unless  it  can  be 
magnilicd  by  putting  in  play  a  reserve  of  force,  as  compressed 
air,  etc.,  improvement  cannot  go  far. 

The  most  hopeful  Held  seems  to  be  the  effecting  a  variation, 
through  a.sensil)lc  range  of  resistance  at  the  sending  end,  to  vary 
the  strength  of  current  in  a  primary  coil  by  shunting  (jr  varying 
the  resistance  of  a  battery  circuit ;  as,  for  example,  a  line  wire 
inserted  more  or  less  in  mercury. 

REMARKABLE    TELEPHONIC    rilEKOMENA.  i 


During  five  evenings  in  the  latter  })art  of  August  and  first 
part  of  Scjitcmber,  1877,  jjcrformcrs  statit)ncd  in  the  Western 
LInion  building  in  New  York,  sang  or  i)layed  into  an  Edison 
musical  tclephouc,  actuated  by  a  powerful   battery,  and  con- 


1  Atistnict  frniii  a  ciiiiiiininioatioii  f'ruiii  Dr.  William  F.  Chaimiiif,',  cifl'roviJuncu, 
II.  I.,  imlili.slit.<i  111  tJiu  Journal  of  the  TcUyntjih,  IJueoiiibur  I'i,  1>J77. 


282 


THE   Sl'KAKlNd    TELKl'HONK. 


Ticotcil  witli  one  or  iiiori'  cilies  l)y  ii  No.  8  gauge  wire,  with 
n-tiirii  tliroii;,^!  tlii' gniuiid. 

Ill  I'nividouct',  on  the  evciiiiijf  of  tlio  first  of  tliese  concerts 
(August  2.'S).  Henry  W.  Vuugluin,  State  assiiyer,  and  the  writer, 
were  eonversiiig  tliroiigli  magneto  telephones  over  usliunt  inudo 
l)y  grountling  one  of  tlie  Anierieaii  District  Telegraph  wires  in 
two  places,  aoout  a  quarter  of  a  mile  a[iart,  thnnigh  suitable 
resistance  coils.     At  about  half  ))ast  eight  o'clock  we  Avere  sur- 

.sed  by  hearing  singing  on  the  line,  at  first  faint,  but  afterward 
becoming  distinct  and  clear.  At  the  same  moment,  apparently, 
Clarence  KathVxtiie,  talking  with  a  frii'iid  through  telephones 
over  a  private  line  in  Albany,  was  interrupted  by  the  same 
sounds.  Afterward,  during  that  and  subsequent  concert  even- 
ings, vririous  airs  were  heard,  sung  by  a  tenor  or  soprano  voice, 
or  played  on  the  coriicL  The  origin  of  these  concerts  remained 
a  my.sterv  for  some  time  in  Providence,  and  the  lines  were 
watched  for  music  many  evenings.  The  programmes  heard 
proved  to  be  ]u-ecisely  those  of  the  Edison  concerts  j)crf()rmed 
in  New  York,  the  singei-s  being  Signor  Tagliai)ictro,  D.  W. 
McAneeny  and  Madame  Belle  Cole. 

The  question  how  this  music  pas.scd  from  the  New  York  and 
Albany  wire  to  a  .shunt  of  the  District  wire  in  Providence,  is  of 
.scientific  importance.  The  Edison  musical  telei)hone  consists  of 
an  instrument  converting  sound  waves  into  galvanic  waves  at 
the  transmitting  station,  and  a  diilerent  instrument  reconverting 
galvanic  into  sound  waves  at  the  receiving  station.  The  battery 
used  in  sending  the  music  from  New  York  to  Saratoga  con- 
sisted of  125  carbon  cells,  with  from  1,000  to  3,000  ohms  resist- 
ance interposed  between  the  battery  and  hue  connections  in 
New  York. 

The  wire  used  in  these  concerts  extended  from  the  "Western 
Union  building,  corner  of  Broadway  and  I)ey  Street,  through 
Park  Row,  Chatham  Square,  the  Bowery  and  Third  Avenue  to 
One  Hundred  and  Thirtieth  Street,  and  thence  via  the  Ilarlein 
itnilroad  to  Albany.  On  the  same  poles  with  this  Albany  wire, 
for  sixteen  miles,  are  supported  no  less  than  four  wires  running 


UEMAHKAIU.K   TKM-M'lKlNIC    I'ltKN'OMEXA. 


2H-d 


villi 


a  I 


tol'rovidoncc,  three  of  tlit'iii  l)ciii^  on  tlm  Puiiio  cros^  ariii,  ami  one 
of  them  heiii<^  Huston  wire  No.  bb  east,  via  Jfartford  ami  I'rovi- 
(leiiio;  a!s(t  for  eight  iiiiU's  a  lifth  wire,  Hostoii  wire  No.  82  east 
via  New  LtJiidoii  ami  J'rovideiiei'.  TlK'.-;e  wire.x,  iiiclmling  the 
Albany  wire,  have  a  eonnnon  ground  eoiniection  at  New  ^'ork, 
and  are  strung  at  the  usual  distani  • .  >art,  and  with  the  ordinary 
insulation. 

At  the  I'rovidenee  end  of  the  H.' ,  ;  ix  New  York  and  l}(jston 
wires,  Nos.  55,  32,  2,  5,  27  and  28  i'uA,  run  into  tlu;  Western 
Union  building,  in  eoinpaiiy  (on  the  same  pules  and  braeket.s), 
for  the  la.st  975  feet,  with  an  Anuriean  Distriet  wire.  This  last 
runs  e.sj)eeially  near  to  wires  55  and  32,  whose  pro.vimity  to  the 
Albany  wire  in  New  York  has  alre.idy  been  traced  idtove.  But 
here  is  a  distiiiet  feature.  TIk;  District  wire  belongs  to  an 
exclusively  air  circuit  of  fou"  and  a  half  miles,  having  no  ground 
connection.  'J'he  New  York  ami  All)any  and  New  York  and 
Boston  wires  are,  or  may  be,  grounded  at  both  ends.  'JMie  Dis- 
triet  circuit  referred  to  in  Providence  is  geograj)hically  two 
circuit;!,  but  electrically  one,  both  working  through  a  single  bat- 
tery 01  fifteen  cells.  Mr,  Vaughan  and  myself  having  District 
boxes  a  quarter  of  a  mile  apart,  on  this  circuit,  made  a  shunt  for 
telephonic  cornnuinication  by  ground  (connection  at  each  house, 
including  several  hundred  ohms  resistance,  so  as  not  to  impair 
the  galvanic  insulation  of  the  line.  The  telephone  talked  through 
this  perfectly,  and  the  sounds  of  aimospheric  electricity  were  heard 
in  remarkable  perfection. 

It  will  be  seen  that  the  music  from  the  Albany  wire  pas.sed 
first  to  two  or  more  2>arallcl  New  York,  Providence  and  Boston 
wires;  second,  from  these  to  a  jiarallel  District  wire  in  Provi- 
dence ;  and  third,  through  a  shunt  of  that  District  circuit  before 
reaching  die  listeners  there. 

This  transfer  of  electric  motion  from  one  wire  to  another  may 
have  taken  place  by  induction,  by  leakage,  or,  in  the  first  instance, 
in  New  Yt)rk,  by  a  crowded  ground  conductor.  In  the  transfer 
in  Providence  from  th(!  New  York  and  Boston  to  the  District 
wii'e,  there  was  no  common  ground  connection,  and  it  is  difiicult 


28-1: 


THE   SPEAKING   TELEPHONE. 


to  suppose  that  sufficient  leakage  toolc  jilacc  on  tlie  three  brackets 
ami  three  poles,  which  were  coiuinoii  1o  the  New  York  and  the 
local  wire,  to  account  for  the  transfer  in  Providence.  Tlic  mag- 
neto-telephone has  also  jiroved  itself  abundantly  capable  of  pick- 
ing up  signals  in  an  adjoining  wire  by  induction  ah  )ne.  Without 
rejecting  wholly,  therefore,  the  other  modes  of  transfer,  T  sliouhl 
ascrilie  to  induction  the  principal  ])art  in  the  transfer  of  tlie  eon- 
certs  from  wire  to  wire  between  New  York  and  Providence. 

What  ])roportion,  then,  of  the  electrical  music,  set  in  motion 
in  New  Ynrk,  could  have  reached  the  listeners  on  the  shunt  in 
I'rovidence?  Whether  induction,  leakage,  or  crowded  ground 
was  concerned,  will  any  electrician  say  that  the  New  York  and 
Pi'ovidencc  wires  situated  as  described,  could  have  robbed  the 
All)any  wire  of  (Uie  tenth  or  even  one  hundrerlth  of  its  electrical 
force  or  motion  ?  When  this  one  tenth  or  one  hundredtli  reached 
Pi'oviilcuco,  will  any  electrician  say  that  the  wires  from  New 
"^'ork.  ill  the  course  of  975  feet,  could  have  given  up  to  the 
parallel  District  wire  one  tenth  or  one  hundredth  of  their  elee- 
tri<'al  wave  motion?  Lastly,  when  the  District  circuit  had  .secured 
tliis  minute  fraction  of  the  original  mu.sic  bearing  electric  waves, 
will  auy  electi-ician  say  that  the  sliunt  as  described  (containing 
600  ohms  resistance,  while  the  shunted  (piarter  of  a  mile  of  Dis- 
trict wire  contained  only  5  ohms  resistance)  could  have  diverted 
one  tenth  of  the  electric  motion  from  the  District  circuit  ? 

The  nnisic  heard  jdainly  in  Providence  did  not,  therefore, 
require  or  use  one  tru  thoiisandtli,  hanlly  one  huii(b(Ml  tliou- 
.siudth,  oC  the  electro-motive  force  originally  imjiarted  to  the 
vVlbany  wire. 

This  startling  conclusion  suggests,  first,  the  wonderful  delicacy 
of  the  magneto-telephone,  on  which  ]ioint  I  shall  vcntun!  to 
enlarge,  and  .second,  the  as  yet  unimagined  capacity  of  electricity 
to  tran.spu.fc  sountl. 

The  magneto-telephone  is  probably  the  most  sensitive  of  clec- 
tro.seopes  for  galv.inie,  magneto-electric,  and  atmospheric  or  free 
(•lectricity,  and  will  be  usimI  extensively  in  .«cii'nce  and  the  arts, 
in  this  capacity.     In  the  French  Academy,  on  the  6th  of  Novem- 


SKXSITIVKXEi^rf   <il-'  THK   TELKPIIOXE. 


285 


hov,  ^[r.  Bivgiu't  iiitroduci'd  the  telc>i)hoiio  as,  of  all  known 
instruments,  opcratiiij^  under  tlic  inilmMice  of  tlie  most  feeble 
electrical  currents.  Prof.  John  I'eirce,  of  Providence,  lias  ascer- 
tained that  the  telephone  gives  audible  signals  with  considerably 
less  than  one  hundred  tliou.sandth  part  of  tlui  current  of  a 
,<inglc  Leelanche  cell.  In  testing  resistances  with  a  Wheatstono 
bridge,  the  telei)hone  is  more  si'iisitive  than  tl;o  galvanometer. 
In  ascertaining  the  eoutinuity  of  line  wire  coil.s  it  gives  the 
readiest  answers.  For  all  the  dillt'rent  forms  of  atmospheric 
electrical  discharge — and  they  are  constant  and  various — the 
telephone  has  a  language  of  its  own,  ando^ieiis  to  research  a  new 
held  in  meteorology. 

A  niagneto-tele[ihone  in  Providence  has  been  found,  under 
very  favorable  conditions,  to  overhear  the  speech  of  another 
niagneto-telejihone  on  a  parallel  wire.  But  it  will  be  noticed  that 
the  nnisie  and  Morse  ojicrating  so  noisily  overheard  on  other 
wii'cs  are  not  pi'odnetsof  tlie  inagnetot(>lc[)lione,  but  of  powerful 
galvanic  currents.  The  delicate  magneto-elcctrio  current  of  the 
tele]ilione  is  not  generally  exposed  to  eavcsdroi)ping,  luiless  dif- 
ferent !-cts  of  wires  actually  come  in  eontacL 

Prof.  Peirce  has  observed  that  if  one  sei'ew-eup  of  a  magneto- 
telephone  is  connected  with  a  ground  wii'e,  in  use  at  the  same 
time  for  Moi-se  operating,  the  Moi-se  signals  will  be  heard  in  the 
telephone,  although  the  other  s<'rew-cup  is  disconnected,  and 
there  is  no  circuit.  Here  the  coils  of  the  telephone  seem  to  be 
momentardy  charged  by  the  pa.ssing  signals,  on  the  principle  of 
a  condenser.  A  still  more  .jving  illustration  of  the  electro- 
scopie  delicacy  of  the  telephone  is  this:  Prof.  E.  W.  Blake,  of 
Brown  University,  talked  with  a  friend  for  some  distance  along  a 
railroad,  using  the  two  lines  of  rails  for  the  telephonic  circuit. 
At  the  same  time  ho  heard  the  operating  on  the  telegraph  wires 
overhead,  caught  by  the  rails,  jirobably  by  induction. 

The  aksencc  of  insulation  in  this  experiment  recalls  another 
curious  observation.  The  telephone  works  better  in  some  states 
of  the  atmosphere  than  in  others.  A  northeast  wind  appears 
specially  favorable.     When  a  storm  is  approaching  the  sounds 


286 


THE  speakinct  telephone. 


arc  sometimes  weak  ;  but  the  tnlking  is  often  lond  and  excellent 
in  the  midst  of  a  storm,  wlien  insulation  is  most  defective.  I 
have  just  verified  this  hy  talking  over  a  short  line  where  the  wire 
is  witliout  insulation,  and  its  oidy  su))port  hetween  two  houses, 
the  trunk  of  a  tree,  just  now  sheeted  with  water  fi-oin  falling 
rain.  Tliis  apparent  indiilcrence  to  insulation  in  a  telephone 
wliieli  will  overcome  a  resistance  of  eleven  thousand  ohms  is  not 
easilv  ex})lained.  This  is  only  one  of  a  multitude  of  paradoxes 
l)rcsented  by  the  telei)hone. 

Tlie  sound  produced  in  the  hOephonc  by  lightning,  even  when 
so  distant  that  only  the  Hash  can  be  seen  in  the  horizon,  and  no 
thunder  can  be  heard,  is  very  characteristic,  somctliing  like  the 
quenching  of  a  droj)  of  melted  metal  in  v/uter,  or  the  sound  of  a 
distant  I'oeket.  The  most  remarkable  circumstance  is  that  this 
sound  is  always  h(>ard  just  before  tlic  Hash  is  seen — that  is,  there 
is  a  ])robablc  disturbance  (inductive)  of  the  electricity  overhead, 
due  to  the  distant  concentration  of  electricity  preceding  the  ais- 
ruptivc  discharge.  On  Sunday,  November  18, 1877,  tliese  sounds 
were  heard  and  remaiked  upon  in  Providence  the  first  time  for 
several  weeks.  The  papers  on  !N[onday  morning  explained  it 
by  the  report  of  thunder  storms  in  Massachusetts  on  the  preceding 
day.  Frequent  sounds  of  electrical  discharge  similar  to  that  of 
lightning,  but  nuu^h  fainter,  are  almost  always  heard  several 
hours  before  a  thunderstorm.  This  has  just  been  exemplilied  in 
Providence. 

The  sounds  produced  in  the  tclciihonc  by  the  auroral  Hashes 
or  streamers  were  observed  in  Providence  by  Prof.  J(jhn  Peirce, 
in  Mayor  June,  1877. 

I  will  give  one  further  illu.stratiou  of  tlu^  delicacy  of  the  tele- 
phone, this  time  in  relation  to  magnetism.  Tn  June,  1877,  Prof. 
E.  W.  Blake  substituted  for  the  magnet  of  the  telephone  a 
bar  of  soft  iron,  free  from  magnetism.  When  this  was  held  in 
the  line  of  the  dipjiing  needle,  the  telephone  talked  readily  by 
the  earth's  magnetism.  Put  when  the  tel(>phon(5  was  swaycil 
into  a  position  at  right  angles  with  the  line  of  the  dipping  needle 
(in  the  same  vertical  ])lane),  it  was  absolutely  silent ;  and  the 


BUEGUETS  TELEPIIONE. 


287 


voice  inoi'easod  or  faded  o\it  in  proportion  as  the  telephone  was 
directed  toward  or  rece<led  from  the  pole  of  the  dipping  needle. 
It  remains  only  to  speak  of  the  rpiality  of  the  concert  music 
overheard  in  Providence.  The  rendering  of  the  music  was  very 
perfect,  but  articulation  was  dellcient  or  absent,  both  in  the 
songs  and  in  some  sentences  which  are  said  to  have  been  de- 
claimed in  New  York  for  the  amusement  of  the  audiences  in 
Saratoga  and  elsewhere.  The  papers  of  the  day  report  that  the 
words  were  undistinguislial)le  in  Saratoga.  There  is,  therefore, 
no  reason  to  suppose  that  tlie  sounds  lost  anything  in  ([uaUty  in 
the  C(jurse  of  their  indii'cct  transmission  to  rrovidence. 


BUE(;UET'S   TELEI'llONE. 


M.  lireguet  has  invented  an  entirely  novel  telephone,  based 
on  the  principle  of   Tiippmann's  elt'ctro-ca),illary  electrometer. 


IX- 


Fig.  133. 

The  transmitter  and  receiver  are  exactly  alike,  and  each  consists 
simply  of  a  glass  vessel  containing  a  layt^r  of  mercury,  over 
which  floats  a  layer  of  acidulated  water.  Into  this  water  dips 
the  point  of  a  glass  tube  containing  mercnry. 

The  uj)per  part  of  the  glass  tube  contains  air,  and  may  be 
open  to  the  atmosphere  orelo.sed  by  a  plate  or  diaphragm  capable 
of  vibrating.  I'lie  circuit  is  formed  by  connecting  the  mer- 
cury in  the  tube  of  the  transmitting  telephone  with  that  in  the 
receiver,  and  also  the  mercury  in  the  vessel  of  the  transmitter 
with  that  in  the  receiver.  When  one  speaks  over  the  top  of  the 
tube  of  the  transmitter,  tlu;  vibrations  of  the  air  are  transmitted 
through  the  mercury  to  the  point  of  the  tube  where  the  mercury 


288 


TUE   SPEAKING  TELEPHONE. 


makes  contact  witli  the  acidulated  water  of  the  vessel  by  the  fine 
capillary  bore  of  the  tul)e.  Here  the  electro-capillary  action 
takes  place,  the  vibratory  motions  of  the  mercury  generating 
electro-cai)illary  currents,  which  traverse  the  circuit  to  the  re- 
ceiver, and  by  a  reverse  process  reproduce  the  air  vibrations  at 
the  top  of  the  tube  of  the  receiver.  M.  Breguet  says  that  this 
telephone,  unlike  Prof.  Bell's,  is  capable  of  reproducing  not  only 
oscillatory  motions  of  the  air,  but  of  reproducing  the  exact  range 
of  the  most  general  movements  of  the  vibratory  plate.  A  port- 
able form  of  this  instrument,  constructed  by  M.  Lippmann,  con- 
sists of  a  fine  glass  tube,  several  centimetres  long,  containing 
alternate  drojts  of  mercury  and  acidulated  water,  so  as  to  form  an 
electro-capillary  series.  It  is  sealed  at  the  ends,  by  which  two 
platinum  wires  make  contact  with  the  terminal  mercury  drops. 
A  rondelle  of  lirwood  is  fixed  normally  to  the  tube  by  its 
centre,  and  gives  a  larger  surface  for  the  voice  to  act  against,  so 
as  to  furnish  more  motion  to  the  tube  when  it  acts  as  a  trans- 
mitter, and  be  easily  ai)plied  to  the  ear  when  it  is  a  receiver. 

M.  Breguet  claims  for  this  teleplume  that  it  will  act  through 
submarine  cables  with  instantaneous  effect,  because  it  will  only 
establish  variations  of  potential  at  the  sending  end  of  the  line, 
and,  unlike  other  telephones,  will  not  generate  currents  to  flow 
through  the  line.  But  this  claim  does  not  apj)ear  to  us  to  be 
justifiable,  since  ciirrents  must  result  in  the  line  from  the  varia- 
tions of  potential  set  uj) ;  and,  if  there  is  to  be  any  communica- 
tion at  all,  they  must  travel  throughout  the  length  of  the  cable 
from  end  to  end. 

REMARKS   ON  THE   THEORY   oP   'I'HE   TELEPHONE. ^ 

It  is  generally  admitted  that  the  audition  of  speech  in  the  tele- 
phone is  the  result  of  repetitions,  by  the  diaphragm  in  the  ;eceiv-, 
ing  instrument,  in  consequence  of  electro-magnetic  effects,  of 
the  vibrations  produceil  in  the   ti,..ismitter   ,.'hen  tiie  voice   is 


J  Ry  Til.  du  Moiiccl.     Extruft  from  Oomptes  RuiiJus  of  tliu  Frciu'li  AciuliMiiy  of 


REMAUKS  OX   TUE   THEORY   OF   THE   TELEPHONE. 


289 


directed  against  its  diapliragm.  If  we  consider  the  effects  pro- 
duced, however,  a  little  retlection  will  show  us  that  this  ex- 
])lanation  can  hardly  be  admitted,  and,  in  addition  to  this,  all 
I'ecent  experiments,  if  not  positively  condemning  it,  seem  at  least 
to  show  that  it  is  incomplete.  It  has,  in  fact,  been  demonstrated 
that  not  only  can  tlie  vibniting  diaphnigm  of  the  telephone  re- 
ceiver be  replaced  by  a  very  thick  and  heavy  armature  without 
thereby  altering  the  transmission  of  speech,  but  it  has  also  been 
shown  that  the  dia2")hragm  may  be  made  of  .some  non-magnetic 
substance ;  and  more  recently  Mr.  Spottiswoode  has  ascertained 
that  the  vibrating  ])late  even  may  be  dispensed  with  without 
l)reventing  telej)lionic  transmission,  if  the  ])olar  extremity  of  the 
magnet  is  placed  very  near  to  the  car.  If  we  consider,  on  the 
other  hand,  that  different  parts  of  the  telephone  may  be  made 
to  transmit  articulate  sounds  cither  directly  or  through  the  inter- 
inediaiy  of  a  string  telcj)hone,  as  shown  by  Mr.  A.  Breguet,  we 
are  led  to  believe  that  the  vibrations  which  re""'Mluce  s[)eech  in 
the  receiver  belong  principally  to  the  magnetic  core  within  the 
bobbin,  and,  consequently,  that  they  !irc  of  the  same  character  as 
those  studied  by  Messrs.  Page,  lEenry,  Wertheim  and  others,  in 
electro-magnetic  bars.  Tlie.<e  vil)rations,  as  is  well  known,  have 
been  utilized  since  1861  in  Rciss's  telephone,  and  more  recently 
in  the  telei)hones  of  Messrs.  Cecil  and  Leonard  Wray,  Yan  der 
Wevde  and  Elisha  Gray.  Under  this  hypothesis  the  vibrating 
diaphragm,  when  actuated  by  the  voice,  lias  no  other  role  to  lill 
than  that  of  generating  induced  currents  in  the  transmitter,  and, 
when  made  to  vibrate  by  the  bar  in  the  receiver,  of  reinforcing 
the  magnetic  effect  of  the  latter  by  reacting  \ipon  its  polar 
extremity. 

Now,  since  the  amplitude  of  these  vibrations  becomes  greater 
as  the  diai)hragm  is  made  more  flexible,  and,  on  the  other  hand, 
liie  variations  in  the  (;lectro-magnetie  state  of  the  plate  tidving 
place  with  increased  rapidity  as  its  mass  is  reduced,  it  will  be 
understood  immediately  why  it  is  im[)ortant  to  use  very  thin 
vibrating  disks.  In  transmission,  greater  amplitude  increases 
the  strength  of  the  induced  currents,  and  in  receiving,  the  varia- 


290 


THK   SPEAKING  'JKl.Kl'HOXE. 


tions  of  magiietiziition  cletonnining  tlie  sounds  arc  I'didorefl 
shar})  and  clear,  and  tlicro  is  cousciiueiitly  an  ailvantagc  in  l)otli 
cases.  Tliis  hypothesis,  it  will  als(j  bo  ohscrved,  in  no  wise 
excludes  the  phonetic  eflects  of  such  mechanical  vibrations  as 
may  be  produced,  and  wliosc  action  would  thei'efore  bo  added 
to  that  in  the  magnetic  cores. 

In  tlie  telephones  of  Messrs.  Reiss,  Wraj  and  Gray,  the  mag- 
netic cores  have  no  armatures  at  all.  sonorous  boxes  alone  being 
used  for  increasing  the  sounds;  but  in  Bell's  telephone  it  is 
more  particularly  the  vibrating  disks  in  the  receivers  which 
determine  the  sound  effect,  and  the  permanent  magnet  is  used 
solely  for  the  purpose  of  rendering  the  apparatus  capable  of 
being  used  both  as  a  transmitter  and  receiver.  In  the  Bell 
model,  shown  at  Phihulelphia,  the  receiver  consisted  simply  of  a 
tubular  magnet,  whose  cylindrical  pole  was  pnn-ided  with  a 
vibrn  ,ing  plate. 

We  have  now  to  ascertain  what  the  physical  effects  are  to 
which  the  vibrations  of  the  magnetic  core,  under  the  influence  of 
variations  in  the  strength  of  the  current  in  the  bobbin,  should  be 
attributed,  and  for  this  )»urpose  it  is  necessary  to  refer  to  the 
experiments  of  Messrs.  Page,  Henry  and  AVerthcim.  P'rom  these 
it  would  appear  that  they  are  due  entirely  to  the  contractions  and 
dilations  of  the  magnetic  molecules  of  the  core,  under  the  influ- 
ence of  successive  magnetization  and  demagnetization  ;  and  this 
assumption  receives  additional  confirmation  from  the  changes 
that  have  been  observed  to  take  i)lace,  by  certain  physicists,  in 
the  length  of  a  bar  of  iron  when  submitted  to  energetic  magnetic 
action. 

As  to  the  more  cfHcacious  action  of  induced  currents  in  tele- 
phonic transmission,  I  do  not  find  it  difficult  to  believe  that  they 
owe  this  advantage  directly  to  their  instantaneous  character  or 
the  suddenness  of  their  production.  For  this  reason,  they  are 
not,  like  voltaic  currents,  dependent  upon  the  duration  of  the 
vibrations  in  the  transmitter;  and,  as  they  do  not  have  to  pass 
through  a  variable  period  either,  which  increases  as  the  square 
of  the  length  of  the  circuit,  their  action  simply  dejiends  upon 


CURRENTS  PRODUCED  IS   THE  TELEPHONE. 


291 


theit"  strength  alone.  They  are,  consequently,  much  more  favor- 
able for  the  production  of  phonetic  vil)ration3  than  voltaic  cur- 
rents; and  tlic  fact  that  the  inverse  currents  which  follow  the 
initial  pulsation  tend  to  diseliarge  the  line  promptly,  contributes 
still  more  toward  rendering  their  action  sharper  and  more  rapid. 
If  we  consider,  also,  that  the  currents  produced  by  the  action 
of  the  voice  on  the  diaphragm  of  an  ordinary  telephone  do  not 
exceed  that  from  a  single  Uaniell  coll  in  a  circuit  of  100  meg- 
ohms resistance,  as  has  been  shown  by  the  researches  of  Mr, 
Warren  de  la  Rue  to  be  the  case,  we  can  readily  understand 
that  the  greater  or  less  strength  of  these  current»s  is  of  little 
importance  in  the  phonetic  elfects  prcxluced,  and,  under  ordi- 
nary circumstances,  would  be  incapal  ;  of  producing  mechani- 
cal movements  or  vibrations  of  sufficient  magnitude  in  a  plate 
like  that  of  the  telephone  to  produce  the  sounds  we  hear. 


CHAPTER  X. 


THK   TALKIXO   I'HONOGBAPH. 

The  Talking  Phonograph,  invented  by  Mr.  Thomas  A.  Edi- 
son, is  a  purely  mechanical  invention,  no  electricity  hcing  used. 
It  is,  however,  somewhat  allied  to  the  telephone,  iov,  lilce  the 
latter,  ita  action  depends  upon  the  vibratory  motions  of  a  metal- 
lic diaphragm,  capable  of  receiving  from  and  transmitting  to  the 
air  sound  viljrations. 

The  term  phonograph,  or  sound-recorder,  includes,  besides  !Mr. 
Edison's,  a  large  number  of  instruments,  whicli,  tliougli  tliey  are 
notable  to  reproduce  sound,  are  capable  of  graphically  represent- 
ing it. 

Before  treating  of  these  instruments,  it  might  be  well  to  recall 
what  has  been  said  in  an  earlier  part  of  this  work  on  the  nature 
of  sound. 

Bearing  in  mind  that  sound  is  and  has  for  its  origin  motion, 
we  will  see  that  a  vibrating  body,  situated  in  an  elastic  medium 
like  our  atmosphere,  becomes  the  central  source  of  a  peculiar 
form  of  action,  which  is  ever  propagated  outward.  This  is 
known  as  wave  motion,  and  if  the  number  of  vibrations  causing 
it  l)e  within  certain  linuts,  the  wave  motion  becomes  jjcrcejitible 
to  the  ear,  and  is  called  sound. 

Any  change  in  the  original  vibrations  will  cause  a  change  in 
the  nature  of  tlie  sound  emitted.  G^hus,  if  their  amphtude  l)e 
increased,  the  soun<l  becomes  louder,  and  can  be  heard  at  a 
greater  distance,  or,  in  otiier  words,  intensity  is  dependent  on 
the  extent  of  the  vibrations. 

Again,  should  the  number  of  vibrations  in  equal  portions  of 
time  be  varied,  the  note  will  rise  or  fall  in  the  musical  scale;  or, 
])itch  depends  on  the  number  of  vibrations  occun'ing  in  a 
given  time. 

A  third  and,  in  this  conneeiion,  more  important  characteristic 


CHARACTEBISTICS  OF  SOUND. 


293 


of  sound  is  that,  while  an  iiiicliaiiging  fundamental  tone  is 
emitted,  other  and  more  rapid  ^■il)l■ali()ns  may  accompany  it, 
on  the  same  ])rincij)Ie  that  the  surface  of  large  ocean  waves  is 
covered  with  smaller  and  independent  rip])lcs.  It  is  the  accom- 
j)aiiinient  and  predominance  of  certain  of  these  harmonics,  as 
they  are  called,  that  gives  to  a  note  that  peculiar  property 
wherchy  it  may  he  distinguished  from  another  of  eipial  intensity 
and  pitch.  This  characteristic  is  often  called  the  timbre  or  color 
of  the  note,  but  is  known  eipially  well  as  its  cpiality. 

The  human  voice  is  the  most  perfect  of  all  musical  instru- 
ments. Certain  parts  of  its  mechanism  can  at  will  be  thrown 
into  vibration,  and  these  vibrations  can  be  varied  in  amplitude 
and  number  at  pleasure.  Associat<;d  with  the  apjiaratus  for 
effecting  this,  is  a  hollow  cavity,  which  serves,  as  does  the  reso- 
nant chamber  of  an  organ  pipe,  to  rcinfi  ce  the  sound.  The 
sha{)e  of  this  cavity  may  be  .so  varied  that  it  will  resound  to 
vibrations  of  any  pitch.  By  means  of  this  latter  jwwcr  we  are 
able  to  produce  the  vowel  sounds.  Accompanying  the  original 
vibrations  are  others  which  are  multiples  of  it,  and  it  is  by  rein- 
forcing one  or  more  of  these  that  the  quality  of  each  vowel  is 
secured.  Thus  the  forcible  cxj)ulsion  of  air  from  the  mouth 
may  give  rise  to  articulate  speech  or  sounds,  whose  shadings  and 
degrees  of  loudness  vary  with  the  number  and  pressure  of  the 
resulting  impulses,  and  also  with  the  degree  of  suddenness  with 
which  they  commence  and  terminate. 

So  rapid  are  the  vibrations  of  a  body  when  emitting  a  sound, 
that  the  eye  and  ear  cannot  discern  all  the  phenomena  which 
accompany  them.  This  has  led  students  of  acoustics  to  devise 
means  of  representing  graphically  the  movements  which  the 
sounding  body  undergoes;  and  it  is  through  the  study  of  these 
drawings  that  much  (jf  our  knowledge  of  the  nature  of  sound 
has  been  obtained. 

One  of  the  .simplest  ways  of  producing  what  we  shall  here- 
after call  the  record  of  a  sound  is  to  <lraw  a  vibrating  tuning 
fork  over  a  sheet  of  ])a])cr,  so  that  a  ])cncil  attached  to  one])rong 
of  the  fork  shall  leave  behind  it  a  waving  line,  as  shown  in  fig. 
134. 


294 


THE   TAI.KlNd    IMtdNoGRAI'Il. 


Witli  tliis  n-uil(i  iirrimjicnicnt  tli(>  cnci'iiy  is  wasted  in  ovor- 
comitiL^  friction,  iind  tiir  fork  soun  cniiu'S  to  fcst.  'I'o  Ji'ssimi  the 
friction  it,  is  usual  to  ciiiitloy  jiapcr  covered  with  a  layer  of  lamp- 
black.  Instead  of  the  jieneil  is  sulistitutcd  a  siuaii  pointed  bristle, 


/Vy.  131. 

the  weight  of  which  is  .so  slijrht  that  it  will  not  inodify  the 
niotiou  of  the  pronjf.  AVith  very  little  force  the  black  can  bo 
removed,  leaving  a  while  line  on  a  dark  ground. 


Fi'j.  135. 

The  nso  of  a  revolving  cylinder,  firound  which  the  pa])or  is 
wrapped,  early  suggested  itself,  and  in  the  liands  of  Duhaniel  the 
apparatus  assumed  the  form  .shown  in  lig.  185.  The  axis  upon 
which  the  drum  revolves  is  a  screw,  which  turns  in  a  lixed  nut, 


Fig.  136. 

causing  the  drum  to  advance  at  each  revolution  through  the 
distance  between  two  consecutive  turns  of  the  thread,  which  i.s 
sufhcient  to  jjrevent  one  portion  of  the  i-econl  from  ])eing  sui)er- 
placed  uj)on  that  which  precedes  it     Fig.  136  shows  the  paper 


SCOTT  S   PHONOfiKAril. 


295 


nftrr  it  liiis  liccii  rciii(>\c(l  iVinii  tin'  cvliiidcr  and  spi-cad  out. 
'l'\\r.  dots,  a,  li,  c,  (■!<•.,  arc  iiiado  Ity  aclix'Ic  wliicli  usually  accdiu- 
|iaiii('S  tli<'  a|i|iai'atus.  'rii(MlistaU(,'0  Ix'tWci'M  tln'iii  iv|i|-cs(>iits  tlic 
duration  (if  oiio  second,  ^riio  amplitude,  and  peculiar  character 
of  each  viliratioii  an!  clearly  ^^howii,  and  to  ascertain  the  rate  of 
xibration  it.  is  only  iiecessury  to  count  the  nuinher  of  umlulationa 
between  two  consecutive  dot.s. 

Devices  have  also  Ihmmi  made  hy  Konijr,  with  wliicli  the  result- 
ant vihrations  arising  from  two  or  more  notes  emitted  .sinmlta- 
neously  may  bo  recorded  directly  from  tlu;  vibnitiiig  bodies. 

The  phono,Lrra|ih  invented  by  M.  Leon  Scott  does  not  require 
that  tracing  shall  be  made  at  the  place  wliere  the  sound  origin- 
ates, but  AvlKM'cver  it  can  b(i  lieiird.  It  consists  of  a  hollow 
ehanibei',  niad(!  sufliciently  largo  to  respond  to  sounds  of  the 
lowest  audible  ])itch,  nKMinted  before  u  eylinder,  similar  to  that 
shown  in  lig.  135.  One  end  of  this  resonator  is  left  open,  and  the 
other  is  terminated  by  a  ring,  on  which  is  iixed  an  elastie  mem- 
brane. The  air  within  the  resonator  i.s  easily  thi'own  into  vibra- 
tion, whieh  is  shared  by  the  membrane.  The  latter  carries  a 
stylus,  which  also  partieipates  in  the  motion,  and  reeords  it  u))on 
the  blackened  2)aper.  The  hinnan  voice,  the  t(nies  from  musieal 
instniments,  and  even  the  rumbling  of  di.stant  thunder  are  thus 
gra])hieally  presented  on  paper. 

For  recording  vocal  iinj)nlses  one  of  the  most  sensitive  instru- 
ments is  the  logograph,  invented  by  W.  11.  Bai'low,  F.  R  S. 

The  pressure  of  the  air  in  speaking  is  directed  against  a 
membrane,  whieh  vibrates  and  carries  with  it  a  delicate  marker, 
which  traces  a  line  on  a  travelling  riljbon.  The  excursions 
of  the  tracer  are  great  or  small  from  the  base  line  which 
represents  the  rpiiet  membrane,  according  to  the  force  of  the 
impulse,  and  are  prolonged  according  to  the  duration  of  the 
pressure,  different  articulate  sounds  varying  greatly  in  length 
as  well  as  in  intensity  ;  another  great  difference  in  them  also 
consists  in  the  relative  abruj^tness  of  the  rising  and  falling  inflec- 
tions, which  makes  curves  of  various  shapes.  The  snioothnes:? 
or  ruggedness  of  a  sound  hi.,i  thus  its  own  graphic  character, 


296 


THE   TALKING   ^IIO^OQRAl'lI. 


independent  both  of  its  actual  intensity  and  its  length.  Tlic 
logograph  consists  of  a  small  speaking  trumpet,  having  an  ordi- 
nary mouth-piece  coiniccted  to  a  tube,  the  other  end  of  which  is 
widened  out  and  covered  with  a  thin  membrane  of  gold  beater's 
skin  or  gutta  perclia,  A  spring  presses  slightly  against  the 
membrane,  and  has  a  light  una  of  aluminium,  which  carries  the 
marker,  consisting  of  a  small  sable  brush  inserted  in  a  glass 
tube  containing  a  colored  licpiid.     An  endless  strip  of  paper  is 

German  r  j'rolonrje*t 

Trnmbone 
uu  in  muod 

Hij.  131. 

caused  to  travel  beneath  the  pencil,  and  is  marked  with  an 
irregular  curved  line,  the  elevations  and  deoressions  of  which 
correspond  to  the  force,  duration  and  other  characteristics  of  t.ic 
vocal  impulses.  The  lines  thus  traced  exhibit  remarkable  uni- 
formity when  the  same  phrases  are  successively  pronounced. 

IncompTthmnihility 

Rg.  138. 

Fig.  137  shows  curves  obtained  by  the  interposition  of  a  light 
lever  between  the  membrane  and  the  smoked  gla.s.s,  wlii(,'h  is 
drawn  a^ong  beneath  the  style,  whose  excursions  are  much  mag- 
nilicd  by  tlic  lever.  The  curves  show  respectively  the  tongue 
trill  or  German  r  ])rolonged,  the  mark  })roduced  by  the  sound  of 
a  trombone,  and  by  the  sound  of  oo  in  mood. 

Fig.  138  shows  a  tracing  from  the  utterance  of   the  word 
incomprehensibility,  with  dillerent  degrees  of  effort.     It  will  be 


I.OGOORAPHIO   RECORDS. 


297 


noticed  that  while  a  certain  variation  occurs,  due  to  the  energy, 
eai'.h  sound  preserves  a  si)ecific  character. 

Kig.  139  sliows  in  tlie  upper  portion  the  cflect  of  words  of 
quantity  which  require  a  largo  vohime  of  air,  and  are  maintained 
a  rehitivcly  longer  time  than  the  more  explosive  or  inten.;e  kind. 

The  lower  diagram  is  what  the  tracer  wrote  when  the  familiar 
stanza  from  Ilohcnlinden  was  repeated. 

A  much   more   delicate  instrunient  for  recording  sonorous 


_xI'vA_ 


JVn(a/iM 


Deducting 


fj 


JJy  turch  ami  Irumitxt  /tmt  arrayeit. 


To  Join   the  drewi/ul  revelry. 

Fig.  139. 

vibrations  has  been  made  by  iisiiig  the  membrana  tympani  of  the 
human  car  as  a  logograph.     This  is  rejirosentcd  in  fig.  140. 

The  stai)es  was  removed,  and  a  short  stylus  of  hay  substituted, 
of  about  the  same  weight,  so  as  to  increase  the  amplitude  of  tlio 
vibrations  and  afford  means  of  obtaining  tracings  upon  smoked 
glass,  as  in  the  logograph  experiments.  The  membrane  is  kept 
moist  by  a  mixture  of  glycerine  and  water,  and  the  specimen 
attached  to  a  perpendicular  bar  sliding  'h  an  upright  post,  and 


298 


THK   TALKING   I'lIOXOfJUAIMI. 


moved  by  a  ratchet  wlieel.  To  tlio  upright  is  attaclicd,  horizon- 
tally, a  iiu'tairu!  stage  six.  inches  in  h'ligtli,  upon  whieli  slides  a 
carriage  with  aghiss  plate,  and  having  a  regular  movement  given 
to  it  by  wheel  and  eord.  A  bell  shajied  mouth-piece  is  inserted 
in  the  external  auditory  meatus  and  luted  in  position. 

Th(^  vibrations  of  the  membrane,  due  to  a  musical  tone  sounded 
ill  the  bell,  may  be  observed  by  means  of  a  ray  of  hght  thrown 


Fi'j.  140. 

upon  .small  specula  of  foil  attached  to  the  malleus,  incus,  or  to 
diil'erent  portions  of  the  membrana  tympani,  or  may  be  recorded 
on  smoked  glass  by  a  stylus  fasteneil  to  the  descending  process 
of  the  malleus  or  incus  by  means  of  glue,  in  a  line  with  the  long 
axis  of  the  pi'oecss,  and  exteniling  downward,  so  as  to  reach  the 
]ilatc  of  smoked  glass,  which  is  moved  at  a  right  angle  to  the 
excursion  of  the  stylus  ;  the  latter  then  traces  a  wave  line  cor- 


KUNIG'S   MOXOXIETKIO   FLAMES. 


299 


responding  to  the  character  uml  pitch  (->f  the  musical  tone 
sounded  into  tlie  car. 

As  the  glass  plates  present  plane  surfaces,  and  as  the  point  of 
the  vihrating  style  sweeps  tlirough  the  segment  of  a  circle,  the 
curves  obtained  are  apt  to  ho  discontinuous,  especially  when  the 
amplitude  is  great.  To  obviate  this  difficulty  a  sheet  of  glass  is 
employed,  having  a  curved  surface,  the  concavity  being  presented 
to  the  stvlus.  The  sheet  of  glass  is  a  section  of  a  cyliniler  whose 
scmi-(liameter  is  C(|uivalent  to  the  length  of  the  style.  In  this 
way  the  point  of  the  stylus  never  leaves  the  surface  of  the  glass, 
and  the  curve  resulting  from  its  vibration  is  continuous.  The 
carbon  lihu  is  preserved  by  pouring  collndiou  upon  it  As  soon 
as  this  is  drv,  the  film  may  be  lloated  off  with  water,  and]ilaced 
upon  a  plane  sheet  of  glass,  or  upon  paj)cr,  and  varnished  in  the 
ordinary  way. 

Numerous  other  methods  of  rendering  sound-vibrations  visilile 
to  the  eve  might  be  cited.  In  general  these  methods  iire  of  two 
kinds.  They  either  aim  at  jirodueing  a  lasting  record  on  paper, 
iiiass,  etc.,  which  may  be  preserved  and  examiiHMl  at  leisure,  or 
they  jiresent  to  the  eve  in  a  vivid  way  the  sound  vibrations  as 
they  arc  actually  transpiring.  Of  the  latter  class,  one  devised  by 
Konig  deserves  a  passing  notice.  A  hollow  chamljcr  is  divided 
by  a  thin  menihrauo  of  caoutchouc  into  two  compartments  :  one 
of  which  communicates  through  a  tube  to  the  mouth-piece,  in 
front  of  which  the  sounds  are  generated;  the  other  is  .supplied 
from  a  pipe  with  ordinary  coal  gas,  which  issues  from  the  com- 
partment through  a  fine  buriu^-,  where  it  is  ignited.  Any  motion 
of  the  diaphragm  will  change  the  ])ressure  on  the  gas,  and  either 
k'Ugtheu  or  shorten  the  jeL  The  movements  of  the  llame  when 
^■iewcd  directly  are  scarcely  perceptible.  To  render  them  dis- 
tinct, they  are  receivi'd  on  a  foui'-sided  mirror,  which  is  made  to 
revolve.  The  image  of  the  ilanie  is  thus  lcugthene(l  out  into  a 
luminous  band.  When  the  membrane  vibrates,  the  upper  edge 
of  the  band  becomes  serrated,  each  elevation  being  due  to  one 
sound-vibration. 

The  instruments  thus  far  desci'ibed,  while    able  to   lu'oduce 


300 


TUE   TALKING   PUONOGliAl'lI. 


rooords  iin(l(inbtc'(lly  convct,  could  jr<>  no  faillici.  1'lie  records 
tlius  made  ,su;i:ge.sti'd  no  way  of  I'eproducing  the  sound.  Hor 
■\vas  tills  elTocted  until  ^Ir.  Edison  produced  liis  wonderful  talk- 
ing phonograj)]]. 

In  its  simplest  form  the  talking  phonograph  consists  of  a 
mounted  diaphragm  (lig.  141),  so  arranged  as  to  operate  u  small 
steel  stylus  ])laced  just  below  and  opposite  its  centre,  and  a  brass 
cylinder,  six  or  more  inches  long  by  three  or  four  in  diameter, 
which  is  mounted  on  a  horizontal  axis,  extending,  each  way, 
beyond  its  ends  for  a  distance  about  equal  to  its  own  length. 

A  spiral  groove  is  cut  in  the  circumference  of  the  cylinder 
from  one  end  to  the  other,  each  spire  of  the  groove  being  sepa- 
rated from  its  neighbor  by  about  one  tenth  of  an  inch.     The 


Fig.  Ul. 

shaft,  or  axis,  is  also  cut  by  a  screw  thread  corresponding  to  the 
s])iral  groo\'e  of  the  cylinder,  and  works  in  screw  bearings;  con- 
se({uently,  when  the  cylinder  is  caused  to  revolve  by  means  of  a 
crank  tli;i''i  is  fitted  to  the  axis  for  the  i)urj)ose,  it  receives  a  for- 
ward or  backward  movement  of  about  one  tenth  of  an  inch  for 
evcr\  tui'u  of  the  same — the  ilirectioii,  of  course,  d'M)ending  upon 
the  way  the  crank  is  turned.  The  diaplu-agm  is  supported  by  an 
ujiright  casting  capable  of  r  '^.istmcnt(lig,  142),  and  so  arranged 
that  it  mav  be  removed  altogether  when  necessary  ;  when  in  use, 
however,  it  is  clamjx'd  in  a  lixed  [)osilion  above  or  in  f rmit  of  the 
cylinder,  thus  bringing  tin;  stylus  always  opposite  the  groove  as 
the  cylinder  is  turned.    A  small  flat  spring  attaelied  to  the  casting 


Morx'iixa  OK  THE  i'hoxocuaph. 


301 


extends  umlcrncath  the  diaphragm  as  far  as  its  centre,  and  car- 
ries the  stylus  ;  and  between  the  diaphragm  and  spring  a  small 
piece  of  india  rubber  is  placed  to  modify  the  action,  it  having 
been  found  that  lictter  results  aro  obtained  by  this  means  than 
when  the  stylus  is  rigidly  attached  to  the  diaphragm  itself.  The 
•dcUon  of  the  apparatus  will  now  be  readily  understood  from 
what  follows.  The  cylinder  is  lirst  very  smoothly  covered  with 
tinfoil,  and  the  diaphragm  securely  fastened  in  place  by  clamp- 
inf  its  support  to  the  base  of  the  instrument.  When  this  has 
been  properly  done,  the  stylus  should  lightly  press  against  that 
part  of  the  foil  over  the  groove.  The  crank  is  now  turned, 
while,  at  the  same  time,  some  one  speaks  into  the  mouth-piece  of 


the  instrument,  which  will  cause  the  diaphragm  to  vibrate ;  and, 
as  the  vibrations  of  the  latter  correspond  with  the  movements  of 
the  air  producing  them,  the  soft  and  yielding  foil  will  become 
marked  along  the  line  of  the  groove  by  a  series  of  indentations 
of  different  depths,  varying  with  the  amplitude  of  the  vibrations 
of  the  diaphragm;  or,  in  otlier  words,  with  the  inllectit)ns  or 
modulations  of  the  speaker's  voice.  These  inflections  may,  there- 
fore, be  looked  ujion  as  a  sort  of  visii)lo  speech,  which,  in  fact, 
they  really  are.  If  now  the  diaphragm  is  removed  by  loosening 
the  clamp,   and  the  cylinder  then  turned  back  to  the  starting 


802 


Tin:  'j'Ai.Kixa  piionogkaph. 


])oint,  \vc  liave  only  to  replace  the  diaj)liragm  and  turn  in  the 
same  clircetion  as  at  first  to  hear  repeated  all  that  lias  been 
spoken  into  the  mouth-piece  of  the  apparatus,  the  stylus,  by  this 
means,  being  caused  to  traverse  its  former  path ;  and,  conse- 
(juently,  rising  and  falling  with  the  depressions  in  tlie  foil,  its 
motion  is  communicated  to  the  diaphragm,  and  thence  through 
the  intervening  air  to  the  ear,  where  tiie  sensation  of  sound  is 
produced. 

As  the  faithful  rcprodnction  of  a  sound  is,  in  reality,  nothing 
more  tiiau  a  reproiluction  <>C  similar  acoustic  vil)raliiins  in  a  given 
time,  it  at  once  bec(jiiu'S  evident  that  the  cylinder  should  be 
made  to  i'cv(jlve  with  absolute  uniformity  at  all  times,  otherwise 
a  diirerence,  more  or  less  marked,  between  the  original  sound 
and  the  reproduction  will  Ixjcome  manifest.  To  secure  this  uni- 
formity of  motion,  ami  ])roduce  a  jtractieally  working  machine 
for  utitomatiially  recording  si)eeches,  vocal  and  instrumental 
mu.sie,  and  jK-rfectly  reproducing  the  same,  the  inventor  lias 
devised  an  ap[)aratus  in  which  a  ])late  replaces  the  cylinder. 
This  plate,  which  is  ten  inches  in  diameter,  has  a  volute  spiral 
gi'oove  cut  in  its  surface,  on  both  sides,  ff(jm  its  centre  to  within 
one  inch  of  its  outer  edge.  An  arm,  guideil  by  the  sj)iral  upcm 
the  under  side  of  the  plate,  carries  a  diaphragm  and  mouth-jjicce 
at  it.s  extreme  end.  If  the  arm  be  ])laccd  near  the  centre  of  the 
plate,  anil  the  latter  rotate<l,  the  motion  will  cause  the  arm  to 
follow  the  spiral  outward  to  the  edge.  A  spring  and  train  of 
wheel-work  regulated  by  a  friction-governor,  serves  to  give  uni- 
form motion  to  the  plate.  Tlie  sheet  upon  which  the  record  is 
made  is  of  tinfoil.  This  is  fastened  to  a  pajicr  fi'amc,  mado  by 
cvitting  a  nine-inch  disk  from  a  square  piece  of  2)aj)er  of  the  same 
limensions  as  the  plate.  Four  pins  upon  the  i)late  ])ass  through 
rresponding  eyelet-holes  punched  in  the  four  cornei-s  of  the 
paper  when  the  latter  is  laid  upon  it,  ami  thus  secure  accurate  re- 
gistration, while  a  clamping-frame  hinged  to  the  ])iate  fastens  the 
foil  an<l  its  paper  frame  securely  to  the  latter.  The  mechanism 
is  so  arranged  that  tho  plate  may  bo  started  and  stopped  in- 
stantly, or  its  motion  reversed  at  will,  thus  giving  the  greatest 
convenience  to  both  speaker  and  copyist 


CO 


TRACINGS   FUOM   PHONOGUAPIIIO   ]{KC()HDS. 


303 


Mr.  Edison  Jia.s  found  that  llic  clearness  of  tlio  instrument's 
articulation  depends  considerably  upon  tlu;  size  and  shape  of  the 
opening  in  the  iiiouth-pieci!.  When  woi-ds  are  spoken  against 
the  whole  diaphragm,  the  hissing  sounds,  as  in  shall,  ileeee,  etc., 
arc  lost  These  sounds  are  rendered  clearly  when  the  hole  is 
small  and  j)rovided  with  sharp  edges,  or  wln'u  made  in  the  ftjrm 
of  a  slot  surr(;nndt'(l  hy  artificial  tectlu 

Beside  tinfoil  other  metals  have  heen  used.  Impressions ]ia\e 
been  made  ujnjn  sheets  of  copper,  and  even  upon  soft  iron. 
Witli  the  copper  foil  the  instruiniMit  spoke  with  sullicient  force 
to  1)0  heard  at  a  distance  of  two  hundi'cd  and  seventy-live  feet  in 
the  open  air. 

liy  using  a  form  of  pantogra]>h.  Prof.  A.  M.  Ikfayer  has  ob- 
tained magnitied  tracings  on  smoked  glass  of  the  record  on  the 


Fi'j.  143. 


foil.  The  a]iparatus  ho  used  consisted  of  a  dcli(;ate  lever,  on  the 
unch-r  siih;  of  which  is  a  ])oint,  made  as  nearly  as  po.ssible  like 
the  jjoint  under  tlie  thin  iron  ])late  in  tla^  jihoiiogra])li.  Cemented 
to  the  end  of  the  long{>r  arm  of  this  lever  is  a  jwinted  slij)  of  thin 
copjter  foil,  wiiich  just  touches  the  vertical  surface  of  a  smoked 
glass  plate.  Tlie  ])oint  on  tlie  short  arm  of  the  lever  rests  in  the 
furrow,  ill  which  are  the  depressions  and  clevation.s  made  in  the 
foil  on  the  (ylindcr.  llotating  the  cylinder  with  a  slow  and  uni- 
form motion,  while  the  ]>late  of  glass  is  slid  along,  the  ])ointof 
cop2)er  foil  scrapes  the  lamjililack  olf  the  smokeil  glass  ])lato  and 
traces  on  it  the  magnilictl  ])ri)lile  of  tlui  deprcssion.s  and  eleva- 
ti(ms  in  thef<iil  on  the  (ylindcr.  In  tig.  143,  vV  represents  the 
aj>])earance  to  the  (ye  of  tlu;  im[)rfssions  on  the  foil,  when  the 
sound  of  a  in  bat  is  sung  again.st  the  iron  ])late  of  the  phono- 


1 


304 


THE   TALKING   I'HONOGKAPH. 


f^nph.  B  is  the  magnified  profile  of  tlicso  impressions  on  tlie 
smolccd  glass  obtained  as  just  described.  C  gives  the  apj)ear- 
anco  of  Konig's  llanie  wiicu  tlie  same;  sound  is  sung  (piite  close 
to  its  membrane.  It  ■will  Ik;  seen  that  the  ])rolile  of  the  inij)res- 
sions  made  on  tlie  phonogra[)h,  and  the  contours  of  the  flames  of 
Kcinig,  when  vibrated  by  the  same  compound  sound,  bear  a  close 
resemblance. 

Mr.  Mayer  finds  that  the  form  of  the  trace  obtained  from  a 
])oint  attached  to  a,  mem1)rane  vibrating  imder  the  inlluence  of  a 
compouml  sound,  de}icnds  on  the  distance  of  the  source  of  the 
sound  from  the  membrane,  and  tlie  same  compound  sound  will 
form  an  infinite  number  of  dill'erent  ti'accs  as  the  distance  of  its 
place  of  origin  I'rom  the  mend)rane  is  gradually  increased  ;  for, 
as  you  incrca.se  this  distance,  the  waves  of  the  comj)onent3  of  the 
compound  sound  are  made  to  strike  on  the  mend)rane  at  dilfer- 
cut  jicriods  of  their  swings.  Vnv  example,  if  the  compound 
sound  is  fornie(l  of  six  harmonics,  the  removal  of  the  source  of 
the  sonorous  vibrations,  from  the  membrane  to  a  distance  eipial 
to  ^  of  a  wave  length  of  the  1st  harmonic,  will  remove  the  2d, 
3d,  4th,  5th  and  (ith  harmonics  to  distances  from  the  mem- 
brane cipial,  respectively,  to  ^,  f.  1.  IJ  and  1^  wavedcngths. 
The  conseipienco  eviilcntly  is,  that  the  resultant  wave-form  is 
entirely  changed  by  this  motion  of  the  source  of  the  sound, 
though  the  sonorous  sensation  of  the  compound  sound  remains 
Tinchangcd.  This  is  readily  prove(l  experimentally  by  .sending 
a  constant  compound  sound  into  the  cone  of  Konig's  a|>pai'atus, 
while  we  gradually  lengtluni  the  tube  between  the  mouth-piece 
and  the  mcndjrane. 

The  articulation  and  quality  of  the  jihonograph,  although 
not  yet  perfect,  is  full  as  good  as  the  telej)hone  was  six  months 
ago.  The  instrument,  when  perfected  and  moved  by  clock 
work,  will  undoubtedly  reproduce  every  condition  of  the  liuman 
voice,  including  the  whole  world  of  exi)ressioa  in  s[)eeeh  and 
song.  The  sheet  of  tinfoil  ur  other  ])lastic  material  receiving  the 
impressions  of  sound  will  be  stereotyped  or  eleetrotyped,  so  as  to 
be  multiplied  and  made  durable ;  or  the  cylinder  will  be  made  of 


APPLICATIONS   OF   Tllf:   PUONOGRAPH. 


305 


a  material  plastic  wlicii  used,  and  hardening  afterward,  Thin 
sheets  of  papier- macho,  or  of  various  substances  which  soften  by 
lieat,  would  be  of  this  character.  Having  jjrovided  thus  for  the 
durability  of  the  phonograph  plate,  it  will  be  very  easy  to  make  it 
separable  from  tlie  cylinder  jjroducing  it,  and  attachable  to  a  cor- 
re.sponditig  cylinder  anywhere  and  at  any  time.  There  will  doubt- 
less be  a  standard  of  diameter  and  pitch  of  screw  for  phonograph 
cylinders.  Friends  at  a  distance  will  then  send  to  each  other 
phonograph  letters,  which  will  talk  at  any  time  in  the  friend's 
voice  when  put  upon  the  instrument.  IIow  startling,  also,  it 
will  be  to  reproduce  and  liear  at  pleasure  tlie  voice  of  the  dead! 
All  of  these  things  are  to  be  common,  evcry-day  experiences 
within  a  few  years.  It  will  be  jjossible  a  generation  hence  to 
take  a  file  of  phonograph  letters,  spoken  at  different  ages  by  the 
same  person,  and  hear  the  early  prattle,  the  changing  voice,  the 
manly  tones,  and  also  the  varying  manner  and  moods  of  the 
speaker — .so  expressive  of  character — from  childhood  up! 

These  are  some  of  the  private  api)lications.  For  public  uses, 
we  shall  have  galleries  where  ])honograph  sheets  will  be  pre- 
served as  photographs  and  books  now  are.  The  utterances  of 
great  speakers  and  singers  will  thci'c  be  kept  for  a  thousand 
years.  In  these  galleries  spoken  languages  will  be  preserved 
from  century  to  century  witli  all  peculiarities  of  pronunciation, 
dialect  or  brogue.  As  we  go  now  to  see  the  stercopticon,  we  shall 
go  to  public  halls  to  hear  these  treasures  of  speech  and  song 
brought  out  and  reproduced  as  loud,  or  louder,  than  when  first 
K[)oken  or  sung  by  the  truly  great  ones  of  earth.  Certainly, 
witiiin  a  dozen  years,  some  of  the  great  singers  will  be  induced 
to  sing  into  the  ear  of  the  phonograph,  and  the  clectrot^'ped 
cylinders  thence  obtained  will  be  put  into  the  hand  organs  of 
the  streets,  and  we  shall  hear  the  actual  voice  of  Christine 
Nilsson  or  Miss  Cary  ground  out  at  every  corner. 

In  public  exhibitions,  also,  we  shall  have  reproductions  of 
the  sounds  of  nature,  and  of  noises  familiar  and  unfamiliar. 
Nothing  will  be  easier  than  to  catch  the  sounds  of  the  waves 
on  the  beach,  the  roar  of  Niagara,  the  discords  of  the  sti     ts, 


HOB 


THE   TALKING   I'HONOGUAPH. 


the  noises  of  animals,  the  puffing  and  rush  of  the  railroad  train, 
of  the  rolling  thunder,  or  even  the  tumult  of  a  battle. 

When  popular  airs  are  sung  into  the  phonograph  and  the 
notes  arc  then  reproduced  in  reverse  order,  very  cui'ious  and 
beautiful  musical  effects  arc  oftentimes  2)roduccd,  having  no  ap- 
parent resemblance  to  those  contained  iu  their  originals.  The 
instrument  may  tims  be  used  as  a  si)rt  of  nmsical  kaleidoscope, 
by  means  of  which  an  inlinite  variety  of  lu^w  combinations  may 
be  })rodu(!ed  from  the  musical  eom])ositions  now  in  existence. 

The  talking  phonograph  will  doubtless  be  applied  to  bell- 
punches,  clocks,  complaint  boxes  iu  puT)lic  conveyances,  and  to 
toys  of  all  kinds.  It  will  supersede  the  shorthand  writer  in 
taking  letters  by  dictation,  and  in  the  taking  of  testimony  before 
referees.  Phonographic  letters  will  be  sent  by  mail,  the  io\\  be- 
ing wound  on  paper  cylinders  of  the  si>;e  of  a  flnger.  It  will  re- 
cite poems  in  tho  voice  of  the  author,  anel  reproduce  the  speeches 
of  celebrated  orators.  Dramas  will  1)0  produced  iu  which  all 
the  parts  will  be  "well  si)oken— with  good  accent  and  good  dis- 
cretion ;"  the  original  rnatriee  being  prepared  on  one  machine 
provided  with  a  rubber  tube  having  several  mouth-pieces;  and 
Madame  Tussaud's  figures  will  hereafter  talk,  as  well  as  look, 
like  their  great  ])rototypesl 

^  The  ])honograpli  has  quite  passed  the  experimental  stage, 
and  is  now  practically  successful  in  every  respect,  and  must  be 
regarded  as  instrumental  in  o})cning  a  i\oW  field  for  scientific 
research,  and  making  one  more  aj)plication  of  science  to  industry. 
Its  aim  is  to  record  and  reproduce  speech,  to  make  a  iierinanent 
record  ot  vocal  or  other  sonorous  vibi-ations,  and  to  recreate 
these  vibrations  in  such  a  manner  that  the  original  vibrations 
may  bo  again  imparted  to  the  air  as  sounds. 

The  tidking  phonograi)li  is  a  natural  outcome  of  the  tele- 
phone, but  unlike  any  form  of  tele2)houe,  it  is  mechanical,  ami 
not  electrical,  in  its  action.  In  using  th(5  jihoiiograph,  it  is  found 
best  to  speak  in  a  loud,  clear  voice,  and  with  distuict  eauneia- 


1  StTibner'a  Monthly  MUj/aziiu,  for  April,  ISTS. 


CHAKACTEKISTICS   OF   TUK   I'HOXOGRAPH. 


307 


tion,  that  the  vibrations  may  lie  sliiirply  ami  deeply  impressed 
on  the  foil.  Attention  must  lie  also  g-j yen  to  the  movement  of 
the  haudle,  so  that  the  ])assage,  of  the  foil  under  the  stylus  will 
be  uuitonu  and  steady. 

As  tlie  speed  of  the  apparatus  decides  the  distance  between 
eaeli  dent  marked  by  llie  sonorous  vibrations,  it  must  also  decide 
the  pitcli  of  the  tone;  when  the  sounds  are  reprodueecL  A  bass 
A'oiee  \v\\}  give  only  half  as  many  vibrations  as  a  soprano  voice, 
one  octave  higher,  and  jirint  half  as  many  marks  on  the  foil  in  a 
given  sj)ace.  If,  in  turning  tiie  instrument  swiftly,  the  speed  at 
which  tliese  marks  pass  under  the  stylus  is  in<;rcased,  then  the 
pitch  of  the  resulting  tones  will  be  raised,  and  the  bass  voice 
may  reapjiear  as  a  soprano,  or  in  a  high,  piping  treble  far  above 
the  pitch  of  any  human  voice.  In  a  t'ontrary  manner,  l)y  turn- 
ing the  handle  slowly,  u  soprano  voice  may  reappear  as  a  very 
deep  bass.  This  curious  circumstance,  in  connection  with  the 
sj^ecch  of  the  phonogi'a])h,  will  undoubtedly  make  it  necessary  to 
employ  clock  work  to  move  the  api)aratus,  in  order  that  an  ab- 
solutely xmiform  rate  of  speed,  and,  consequently,  rate  of  vibra- 
tion, may  be  ])reserved  while  the  machine  is  m  operation.  The 
foil,  after  having  been  iniiiressed  with  the  vibrations,  presents  a 
regularly  lined  or  scored  ap})earaiice.  But  so  minute  are  the  in- 
dentations stamp)ed  in  the  groove  that  they  can  hardly  be  seen 
without  a  glass.  The  foil  is  quite  soft,  and  is  liable  to  injuiy, 
and  it  is  proposed  to  make  Hter(H)tyjie  copies  of  the  projier  size 
to  fit  the  cylinder  of  the  plionogra[)li.  Such  cylinders  will  be 
}iermanent  and  durable,  and  can  be  used  many  times  over  with- 
out injury,  or  can  be  duplicated  by  electrotvping.  The  tone  of 
the  phonograph  is  usually  rather  shrill  and  pi^'ing,  but  this  de- 
fect will  vmdoubtcdly  be  correct(?d  by  improved  instruments.  It 
must  be  observed  that,  marvellous  as  this  instrument  is,  it  is  still 
quite  new,  and  it  is  impo.ssible  to  say  to  what  degree  of  perfec- 
tion it  may  yet  bo  carried.  It  has  already  ojtened  the  door  to 
an  entirely  new  and  nntrie<l  field  in  the  jtliysies  of  sound.  It 
is  a  new  instrument  in  the  liaiids  of  science  wherewith  to 
search  out  yet  unknown  laws  in  nature.     Already  it  has  sug- 


808 


THE  TALKING   PHONOGKAPH. 


gostcd  many  valuable  uses  in  tracV,  munufactnrcs  and  social 
life,  and  it' will  bo  the  aim  of  tliis  depurtnient  to  report  the 
pro-rress  of  this,  one  of  the  most  remarkable  inventions  of  this 
century,  and  its  applications  to  science  aud  industry. 


social 
)rt  the 
j£  this 


CITAFrER  XI. 


QUADKUl'LEX   TKLKGUAl'UY. 

The  qnadrnplcx  system  of  tclcgrapliy,  by  moans  of  which  four 
communications,  two  in  each  direction,  may  be  simultaneously 
transmitted  over  a  single  wire,  has,  within  a  few  years,  found 
very  cxtensiyc  practical  applic^ation  n\)on  the  lines  of  the 
Western  Union  TelcLn-aph  Com])any,  and  is  at  thi^  pr(>sent  time 
operated  npon  sixty  eii'cuits,  between  almost  all  (jf  the  principal 
cities  in  the  country. 

The  distinguishing  principle  of  this  system  consists  in  com- 
binin^at  two  terminal  stations,  two  distinct  and  unlike  methods 
of  single  transmission,  in  such  a  manner  that  they  may  be 
carried  on  independently  upon  the  same  wire,  and  at  the 
same  time,  without  interfering  with  each  other.  One  of  these 
methods  of  single  transmission  is  known  as  the  double  current 
system,  and  the  other  is  the  single  current  or  open  circuit  system. 
In  the  doul)le  current  system  tlu;  battery  remains  constantly  in 
connection  with  the  line  at  the  sending  stations,  its  polarity 
being  completely  revers(>d  at  the  beginning  and  at  the  end  of 
every  signal,  without  breaking  the  circuit.  The  receiving  relay 
is  providtxl  with  a  polarized  or  ]iermanently  magnetic  armature, 
but  has  no  adju.sting  spring,  and  its  action  depemls  solely  upon 
the  reversals  of  polarity  ujion  tlie  line,  withmit  reference  to  the 
strength  of  tlie  current.  In  the  single  cui-rent  system,  on  the 
other  hand,  the  transmissicm  is  effected  by  increasing  and 
decreasing  the  current,  while  the  relay  may  have  a  neutral  or 
soft  iron  armatur(>,  provided  with  a  retracting  spring.  A  better 
form,  however,  for  long  circuits,  is  that  of  the  polarized  relay, 
especially  adapted  to  prevent  interferences  from  the  reversals 
sent  into  the  line  to  operate  the  double  current  system.  In  this 
system,  therefore,  the  action  dci)ends  solely  upon  the  strength 


310 


Q  IT  AUK  r  r  L  K  X  T  K  LK<i  U  APII Y. 


of  tlic  current,  its  jiolarity  being  ultogetlior  ii  nmtter  of  indillVr- 
unco 

It  will  thus  1)0  apiiiirciit  tliut  by  making  use  of  tlicsc  two 
distinct  qualities  of  the  current,  vi/.,  polarity  and  strength,  com- 
bined with  the  dnjiU'X  ]irincijil(!  of  simuluincous  trunsmissiou  in 
o]i]iosit(!  directions,  four  sets  of  instruments  may  lie  (,])cra;..l  at 
the  same  time,  on  the  same  wire.  This  method  p  )sscsscs,  more- 
over, tlie  important  jjractical  advantage  tliat  tlie  action  of  ea(;li 
of  the  receiving  relays  is  [icrfcctly  independent  P^ach  receiving 
ojierator  controls  his  own  relay,  and  can  adjust  it  to  suit  himself 
without  interfering  with  the  other. 

Fig.  144  shows  the  quadruplex  apparatus,  as  arranged  ujion 
the  bridge  jilan,  which  was  at  first  emi)loyeil  bv  the  Western 
Union  Telegraph  Comjiany  in  1874,  when  the  systeni  was  j)lace(l 
upon  its  lines. 

Tj  is  a  double  current  transmitter  or  })ole-clianger,  operated 
by  an  electro-magnet,  local  battery  Cj  and  finger  key  Kj.  The 
office  of  the  transmitter  Tj  is  simj)ly  to  interchange  the  ])oles  of 
the  main  battery  Ej,  with  respect  to  the  line  and  ground  wires, 
whenever  the  key  Kj  is  depressed;  or,  in  other  words,  to  reverse 
the  polarity  of  the  (Mirrent  upon  the  line  by  reversing  the  poles 
of  bat*ery  Ej.  By  the  use  of  properly  arranged  .spring  contacts, 
s,  5,,  ibis  is  done  without  at  any  time  interrupting  the  circuit 
Thus  the  movements  of  the  transmitter  Tj  cannot  alter  the 
stren^t.b  of  the  current  sent  out  to  line,  l)ut  only  its  polarity  or 
direction.  The  second  transmitter,  Tj,  is  operated  by  a  local 
circuit  and  key  Kj  in  the  same  manner.  It  is  coiniected  with  the 
battery  wire  12,  of  the  transmitter  Tj,  in  such  a  way  that  when  the 
key  Kg  is  dej)ressed,  the  battery  Ej  is  enlarged  by  the  addition 
of  a  second  battery.  Eg,  of  two  to  three  times  the  number  of 
cells,  by  means  of  which  it  is  enabled  to  send  a  current  to  the 
line  of  three  or  four  times  tlie  original  strength,  but  the  polarity 
of  the  current  with  respect  to  the  line  of  course  still  remains,  as 
before,  under  control  of  the  first  transmitter  Tj. 

At  the  other  end  of  the  line  are  the  two  receiving  instruments 
Rj  and  R3.     R^  is  a  polarized  relay  with  a  permanently  mag- 


BKIUGK  MKTHOD. 


311 


Icr- 


-m 


812 


gUADRUPLEX  TELEGRAPHY. 


nctic  armaturo,  wliicli  is  dcflectod  in  one  direction  b\'  positive, 
and  in  the  otlicr  hy  nc<rativc  cvn-rents,  without  reference  to  their 
Rtrenjxth.  This  relay  consequently  responds  solely  to  the  move- 
ments of  key  Kj,  and  operates  the  sounder  Sj  by  a  lo(;al  circuit 
from  battery  Lj  in  the  usual  manner.  Relay  Rg  is  placed  in  the 
same  main  circuit,  and  is  })rovided  with  a  neutral  or  soft  iron 
armature.  It  res})onds  with  equal  readiness  to  currents  of  (uther 
polarity,  provided  they  are  strong  enough  to  induce  sufficient 
magnetism  in  its  cores  to  overcome  the  tension  of  the  opposing 
annaturo  spring.  The  latter,  however,  is  so  adjusted  that  its 
retractile  force  exceeds  the  magnetic  attraction  induced  by  the 
current  of  the  battery  Ej,  but  is  easily  overpowered  by  that  of 
the  current  from  Kj  and  Eg  combined,  which  is  three  or  four 
times  as  great.  Therefore,  the  relay  Eg  responds  only  to  the 
movements  of  key  Kg  and  transmitter  Tg. 

The  same  diiriculty  which  troubled  fonner  inventors  arises 
again  in  this  coiuiection.  When  the  polarity  of  the  current 
iqiou  the  line  is  reversed  during  the  time  in  which  the  armature 
of  Rj  is  attracted  to  its  poles,  the  armature  will  fall  oil"  for  an 
instant,  owing  to  the  cessation  of  all  attractive  force  at  the 
instant  when  the  change  of  polarity  is  actually  taking  place,  and 
this  would  confuse  the  sigiuils  by  false  breaks  if  the  sounder 
were  connccteil  in  tlic  ordinary  way.  By  the  arrangement  shown 
in  the  figure,  the  armature  of  the  relay  Rg  makes  contact  on  its 
back  stop,  and  a  second  h)cal  battery  Lj  operates  the  receiving 
sounder  Sg.  Thus  it  will  be  understood  that  when  relay  R„ 
attracts,  its  armature,  the  local  circuit  of  soun<ler  Sg  will  be 
closed  by  the  back  contact  of  local  relay  S;  but  if  the  armature 
of  Rg  falls  off,  it  must  reach  its  back  contact,  and  remain  there 
long  enough  to  comjjlete  the  circuit  through  the  local  n^lay  S 
and  02)erale  it  before  the  sounder  Sg  will  be  all'ected.  But  the 
interval  of  no  magnetism  in  the  relay  Rg,  at  tiie  change  of 
polarity,  is  too  brief  to  ])ermit  its  armature  to  remain  on  its  back 
contact  long  enough  to  alfect  tiic  local  relay  S,  and  through  the 
agency  of  this  ingenious  device  the  signals  from  K,  are  proj)erly 
resi)onded  to  by  the  movements  of  sounder  Sg. 


BRIDGE   MKTIIOD. 


313 


By  placing  the  two  receiving  instmmcnts  R^  and  Rg  in  tlie 
bridge  wire  of  a  Whcatstone  balance,  and  duplicating  the  entire 
aj)paratiis  at  eacli  end  of  the  line,  tlie  currents  transmitted  from 
either  station  do  not  affect  the  receiving  instruments  at  that 
.station.  Thus  in  iig.  144  the  ke^-s  K^  and  Kg  are  supposed  to 
Ijc  at  New  York,  and  their  rnovements  are  responded  to  only  by 
the  receiving  relays  R,  and  Rj  at  Boston.  Tlie  duplicate  parts 
which  are  not  lettered  operate  in  precisely  the  same  manner, 
but  in  the  opposite  direction  with  respect  to  the  line. 

In  aj)plying  this  system  of  quadrupiex  transmission  upon  lines 
of  considerable  length,  it  was  found  that  the  interval  of  no  mag- 
netism in  the  re(>eiving  relay  Rg  (which,  as  before  .stated,  takes 
place  at  everv  reversal  in  the  jjolarity  of  the  line  currcMit)  was 
givatlv  lengtliened  by  the  action  of  the  static  discharge  from  the 
line,  so  that  the  employment  of  the  local  relay  S  was  not  suffi- 
cient to  overcome  the  difficulties  arising  therefrom.  A  rheostat 
or  ivsistanee  Xj  was  therefore  placed  in  the  bridge  wire  with  the 
receiving  instruments  R^  and  Rg,  and  shunted  with  a  condenser 
cof  considerable  capacity.  Between  the  lower  plate  of  the  con- 
denser and  the  junction  of  the  bridge  and  earth  wire  an  addi- 
tional electro-magnet  r  was  ]ilaced,  acting  upon  the  armature 
lever  of  the  relay  R^,  and  in  the  same  sense.  The  eifect  of  this 
ari'angement  is,  that  when  the  cun-ent  of  one  polarity  ceases,  the 
condenser  c  immediately' discharges  through  the  magnet  r,  which 
acts  upon  the  armature  lever  of  relay  Rg,  and  rc!tains  it  in  posi- 
tion for  a  brief  time  hefore  the  current  of  the  oppo.site  polarity 
arrives,  and  thus  serves  to  bridge  over  the  interval  of  no  mag- 
netism between  the  currents  of  opposite  polarity. 

It  will  be  seen  that  the  cond)iuation  of  transmitted  currents  in 
this  method  differs  materially  from  any  of  thos(>  u.sed  in  previous 
inventions.     The v  are  as  follows: 


1.  When  the  first  key  is  closed  and  the  second  open,  -t~  1 

2.  When  the  sec'ond  key  is  closed  ami  the  lirst  open  —  3  or — 4 

3.  When  both  keys  are  closed -|-3  or-|-4 

4.  When  both  keys  are  o[)en —  1 


314 


QrADuri'j.j-Lx:  telegraphy. 


Here  we  discover  another  very  important  practical  advantage 
in  the  system  under  consideration,  which  is  due  to  the  fact  tliat 
the  dili'erenee  or  working  margin  between  the  strciigtlis  oi"  cur- 
rent required  to  produce  signals  upon  the  polarized  relay  and 
upon  the  neutral  relay,  respectively,  may  be  increased  to.  any 
extent  which  circumstances  render  desirable.  Within  certain 
limits,  the  "Teater  this  diflerence  tlie  better  tiie  iriictical  results, 
I'or  the  reason  tliat  the  range  of  adjustm  ,■  v.  o  ■  neutral  i-elay 
increases  directly  in  projtortion  to  the  nu.  u,  .e  ratio  of  the 
resjiective  currents  has  l)een  gradually  increased  from  1  to  2  to 
as  high  as  1  to  4,  with  a  corresponding  improvement  in  the 
jiractical  opei-ation  of  the  apparatus. 

From  what  has  been  said,  therefore,  it  will  be  seen  that  before 
it  became  possible-  to  produce  a  quadruplcx  ajiparatus  capable 
of  being  worked  at  a  commercial  rate  of  speed  upmi  long  lines, 
it  was  essential  that  its  component  parts  slioiild  have  arrived  at 
a  certain  stage  of  development  When,  in  the  early  part  of  1872, 
simultaneous  transmission  in  opposite  directions  was  for  .the  first 
tune  rendered  j)ractieable  upon  long  lines  by  the  cond)ination 
therewitli  of  the  condenser,  the  first  step  was  accomplished.  It 
now  only  remained  to  invent  an  equally  successful  ni'Ml'od  of 
simultaneoiis  transmission  in  the  same  direction,  wl-  v.ii,  .s  we 
have  seen,  was  done  in  1874.  The  application  of  o  •  ^''.ore 
of  the  existing  duplex  eond)inations  to  the  new  ''(.  .' .  <^^.  o 
iorm  a  quadruplex  apparatus,  soon  followed  as  a  nut. '.  of 
course. 

The  following  method  of  simultaneous  transmi.ssion  in  the 
same  direction  was  inven.ted  in  December,  1875. 

Fig.  145  is  a  diagi'am  of  the  ajniaratua  as  ai'rangod  for  quadru- 
plex transmission.  The  lever  t^,  witli  its  appendages,  constitutes 
the  first  or  single-point  transmitter,  wliich  is  the  same  as  that  of 
the  Stearns  duj)lex,  being  operated  by  an  electro-magnet  Tj,  local 
battery  <  and  key  Kj.  The  second  or  double-jvn  !  transmitter 
consists  of  a  quatlranguliir  jilato  of  hard  rubl  l;  '•,  mounted 
u])on  an  axis,  and  capable  of  being  oscillated  by  tue  ana  c, 
which  is  rigidly  attached  to  it     By  means  of  a  spring  e^,  the 


DIFFERENTIAL   METHOD. 


815 


arm  e  prespos  upon  a  roller  fixed  upon  one  end  of  the  lever  fZ, 
which  forces  the  otlier  end  of  the  lever  against  the  stop  d^.  The 
k'\'er  d  carries  the  armature  of  the  electro-magnet  Tg,  which,  like 
the  single  point  transmitter,  is  operated  by  a  local  hattery  and 
key  Kn.  The  oscillating  plate  E  has  four  insulated  contact 
pointsy;  g,fi,  ffiy  upon  its  respective  angles.  The  contact  levers 
F  and  G  are  mounted  on  axes  at  each  end  of  the  plate  E,  and 


Fi>j.  145. 

arc  pressed  against  it  liy  springs  Sj  s^.  When  the  transmitter  is 
in  a  position  of  rest,  as  shown  in  the  ligure,  F  is  in  contact  with 
/and  G  with/,,  and  the  iiarts  arc  kept  in  this  position  l)y  the 
action  of  the  spring  c,.  When  key  Kg  is  dcjircssed,  the  arm  e 
is  raised  by  the  action  of  the  electro-magnet  Tg  npcm  the  bent 
lever  d  :  this  turns  the  ])lato  E  upon  its  axis,  and  brings  F  into 
contact  witli  y  and  G  with  f/^. 


316 


QrADRl'PLEX  TEIiEGHAPIlT. 


In  tliis  apparatus,  as  in  the  one  previously  doscribod,  there  are 
four  (liHereut  electrical  conditions  possible  when  transmitting 
two  sinudtancous  dospatclics  iu  tlic  same  dinx-tion,  as  follows: 

1.  Botli  keys  in  a  jjosition  of  rest.  Tliis  position  is  represented 
in  fig.  145.  Disregarding  for  the  present  the  receiving  instru- 
ments and  their  connections,  the  circuit  may  be  traced  as  follows: 
Fi-om  the  earth  at  G  through  wires  9  and  8,  contact  spring  h, 
lever  ^j,  wire  7,  contact  ])ointy"i  and  lever  G,  wires  G  and  5,  and 
thence  through  the  receiving  instruments  to  the  line  L.  Thus 
the  line  wire  is  connected  to  earth  without  any  battery,  and  there 
is  no  current  upon  the  line. 

2.  The  first  key  closed  and  the  second  hey  open.  Tlie  route  is  the 
same  as  before  from  the  earth  .it  G  to  contact  s])ring  h.  From 
this  point  it  now  diverges  through  contact  l<n-er  F,  wires  12,  13, 
and  battery  B  to  wire  7,  and  thence  to  the  line  as  before.  The 
battery  B  is  now  iu  circuit  and  scuds  a  -f-  current  to  line. 

3.  The  second  key  closed  and  the  first  Jcey  opeji.  The  route  is  now 
from  the  earth  at  G,  through  wires  9  and  8,  contact  spring  b  and 
lever  t^,  as  in  the  llrst  instance,  thence  through  battery  B,  wires 
18,  12,  contact  lever  G,  wires  (!,  6,  and  through  the  receiving 
instruments  to  line.  'I'lic  sunie  buttery  B  now  sends  a  —  current 
to  the  line. 

•i.  Jhth  keys  closed.  The  route  is  now  from  the  earth  at  G,  by 
wires  9  and  8  to  contact  spring  h  ;  tiieuee  by  contact  point  a  and 
wire  14  to  battery  3B;  thence  by  wire  15,  through  //  +.)  lever  F, 
wire  12  anil //j  to  contact  lever  G,  and  tiually  through  wires  H 
and  5  to  the  line.  The  battery  3B,  which  contains  about  three 
times  as  many  eliMnents  as  B,  now  sends  a  -j-  eiirrent  to  the  line. 
It  will  thus  be  seen  that  the  two  battei'ies  V>  and  3B  are  n(!V(!r 
thrown  together  on  the  line  at  the  same  time,  as  in  tlii"  previous 
arrangement 

The  receiving  apparatus  consists  of  two  sounders,  S,  and  Sj, 
which  are  controlled  1)}'  two  relays,  Hj  and  \{„,  fig.  1-15.  I'he 
line  wire  Ij,  on  entering  the  receiving  station,  jiasses  tiu'ough  tlie 
coils  of  both  relays,  and  thence  to  earth  through  the  transmitting 
apj)aratus.     Both  relays  are  pro\-idcd  witli  polarized  armatures. 


DIFFERENTIAL    METHOD. 


817 


and  are  preferably  constructed  with  two  electro-magnets  m  Wj, 
arranged  with  their  poles  lacing  each  other,  with  a  permanently 
magnetized  armature  between  the  (opposite!  ])ules. 

The  arriving  current,  entering  the  I'clay  Jlj,  passes  through 
the  wire  2  and  coil  /t,  of  magnet  m  and  h^  of  in^,  which  are  so 
arranged  that  a  -\-  current  will  cause  the  jtolarized  armature  n  to 
be  attracted  by  ??ij  and  repelled  by  m,  while  with  a  — ■  current 
the  opposite  efl'cet  will  be  produced. 

The  armature  of  relay  llj  is  provided  with  a  retracting  spring 
i\,  and  operates  the  sounder  Sj  by  means  of  a  looid  battery  /j.  in 
the  ordinary  manner.  The  rehu'  Rj  consists  of  two  electro- 
magnets p  and  ^^j,  and  its  armature  is  also  provided  with  a  re- 
tra(!ting  spring  r^  ;  l)Ut  it  differs  materially  from  the  other  relay 
in  the  arrangement  of  its  local  connections.  The  polarized  arma- 
ture o  is  held  by  the  tension  of  the  spring  r^,  not  against  a  fixed 
stop,  but  against  the;  free  end  of  a  movable  contact  lever  r,  the 
opposite  end  of  which  turns  upon  an  axis.  The  contact  lever  r 
is  itself  held  against  a  fixed  stop  q  by  a  spring  7,,  the  tension  of 
which  considerably  exceeds  that  of  spring  r^.  The  local  battery 
to  is  placed  in  the  wire  22,  leading  from  the  contact  lever  r  to 
the  differential  sounder  Sj. 

The  manu'T  in  which  the  receiving  instruments  operate  in 
each  of  the  four  different  electrical  conditions  of  the  lino  is  as 
follows : 

1.  No  current.  The  local  circuit  of  sounder  Sj  is  kept  open 
by  the  action  of  spring  r^  on  armature  ?i,  ami  it  remains  inactive. 
The  opposing  branch  circuits  23  and  2-1:  of  sounder  S3  arc  Ijoth 
closed  by  relay  Hj,  which  render  it  also  inactive. 

2.  Current  of  -\-  V>.  The  relay  Rj  (which  is  affected  by 
positive  currents  of  any  strength)  o[)erat(>s  sounder  Sj.  The 
armature  of  relay  Rg  is  pressed  more  strongly  against  contact 
lever  r,  but  not  with  safhcient  power  to  overcome  the  spring  q^. 
Sounder  Sg  is  therefore  unaffected. 

3.  Current  of — B.  The  armature  of  relay  R,  is  attracted 
toward  its  back  stop,  and  S,  is  not  affecte<l.  The  armature  of 
Rj  is  attracted  to  the  right,  and  oj)ens  wire  24,  which  permits 


318 


QUADKUPLKX  TKLEGRAl'HY. 


the  local  battery  to  to  operate  tlie  sounilei-  S„  liy  way  of  wires  22 
and  23. 

•i.  Current  of -\-  3B.  Tlio  armature  of  relay  E^  operates  as 
in  tlie  second  case.  The  increased  power  of  tlie  curi-cnt  from 
the  batter}' of  many  elements  causes  the  armature  of  ]{„  to  over- 
come the  resistance  of  sprini^f  </j,  and  brcaic  tlie  local  circuit  of 
■wire  22,  leaving  the  sounder  Sg  free  to  operate  by  way  of  wires 
22  and  24.     Thus  the  -\-  3B  current  operates  both  sounders. 

In  order  to  adapt  this  system  to  quadruplex  transmission,  addi- 
tional helices  li  h^  and  h^  h^  are  })laced  upon  the  receiving 
relays  Rj  and  llg,  which  are  placed  in  the  circuit  of  an  artificial 
line,  arranged  according  to  Stearns's  differential  duplex  method, 
■which  diverges  at  the  point  5  and  goes  by  way  of  10,  17,  18,  10, 
20  and  21  to  the  earth  at  G,  and  is  provided  ■with  the  usual 
rheostat  X  and  ct)ndcnser  C.  The  small  rheostat  a;  is  employed 
to  regulate  the  time  of  discharge  from  the  condenser. 

By  the  arrangement  of  the  contact  lever  r,  in  connection  with 
the  armature  lever  o  of  relay  Rj,  and  the  local  circuits  as  above 
described,  the  reversal  of  polarity  upon  the  line  takes  place 
without  interrupting  the  signal  upon  sounder  Sg,  ior  the  reason 
that  when  the  armature  o  is  acted  upoi\  b\''  the  reversal  it  goes 
directly  over  from  one  extreme  position  tc^  the  other,  ■without 
stopjiiug  at  the  intermediate  position  long  enough  to  affect  the 
sounder  Sj,  even  if  there  is  a  considerable  interval  l)etwccu  the 
successive  curi-cnts. 

An  improvement  upon  the  above  arrangement  was  subse- 
quently invented,  in  which  an  entirely  novel  combination  of 
currents  upon  the  line  was  employed,  and  which  docs  not  require 
the  polarity  of  the  current  to  bo  reversed  tluring  the  transmission 
of  a  signal.  In  lig.  146,  Tj  is  a  local  electro-maguct,  whi(;h  oper- 
ates the  single  pc^int  transmitter  ^j,  under  control  of  the  key  Kj. 
The  key  Kg  in  like  manner  controls  the  double  point  trans- 
mitter <2.  The  four  electrical  conditions  of  the  line  in  the  dif- 
ferent ]iositions  of  the  keys  are  as  follows: 

1.  Both  keys  open.  This  is  the  ])i)sition  represented  in  the 
figure.     The  route  of  the  current  is  from  the  earth  at  G,  through 


DIFFERENTIAI,   METHOD. 


819 


wire  1,  sprii\t,f  />,  lever  t^,  wires  2  and  3,  coutact  jioint  o,  spring O, 
wires  4  ami  5,  battery  li,  wires  G  ami  7,  contact  pDint  ?;,  and 
spring  Tn,  tlienee  hy  ^viro  8  to  line  L.  Tlie  IjattiM-y  B  sends  a  -\- 
current  to  line. 

2.  First  hy  closed  and  second  Icey  open.     Tlie  route  is  now 


^  1 


hiii|iii|i|iiiiiiiiiiiii^ 


3B 


Fig.  14G. 


from  earth  at  G,  by  wire  1  and  spring  h  to  point  a,  wires  12  and 
7  and  thence  as  before  to  the  line.  lu  this  case  there  is  uo 
battery  in  eireuit,  and  uo  current  goes  to  line. 

3.  Second  h-y   cloned  and  first  by  open.     Tlie  route  is  now 
from  earth  at  G  by  wire  1,  spring  h  and  lever  t^,  wires  2  and 


320 


QUADRU  IT.KX   TKLEURAPHY. 


13,  battciy  3H,  wire  14,  jioiiit  Oj,  spring  O.  wires  4  and  15,  con- 
tiict  point  II  ^,  wj)ring  N  and  wire  8  to  tlie  Jinc.  Tlie  large  bat- 
tery 3B  semis  a  —  current  to  the  line. 

4.  Both  keya  closed.  The  route  is  from  earth  at  G  by  wire 
1,  spring  I),  ccjutuct  ])oint  a,  wires  12  and  6,  main  battery  B, 
wires  5  and  15,  contact  point  n^,  spring  N,  and  wire  8  to  hue 
L.  In  tliis  case  the  lesser  main  battery  sends  a  —  current  to 
line. 

The  receiving  apparatus  consists  of  two  sounders  S^  and  S3, 
controlled  by  two  relays  11^  and  Eg.  both  of  wdiich  have  polar- 
ized armatures,  and  are  constructed  in  the  same  manner  as  those 
described  in  connection  witli  the  la.st  method.  The  armature  of 
relay  Rj  is  jjrovided  with  a  retracting  spring  rg,  and  o])crates 
the  sounder  S3  by  means  of  a  local  battery  Z^,  in  the  usual  man- 
ner. The  polarized  armature  7,  when  no  current  is  ])assing 
through  the  line,  is  held  by  a  spring  i\  against  the  free  end 
of  a  contact  lever  r,  which  is  in  turn  held  against  tlie  fixed 
stop  q  by  the  tension  of  a  spring  (/j,  which  considerably  exceeds 
that  of  the  spring  r^. 

The  manner  in  which  the  receiving  instruments  operate  in 
each  (jf  the  four  conditions  of  the  line  is  as  follows:  1.  Cur- 
rent of-\-  B.  The  local  circuit  of  sounder  Sj  is  kept  open  by 
the  action  of  the  positive  current  upon  the  polarized  armature  of 
relay  Ei,  which  is  suflicicnt  to  overcome  the  tension  of  s})ring 
rj,  and  it  therefore  remains  inactive.  The  local  circuit  of 
sounder  Sg  is  kept  open  by  the  action  of  the  positive  current 
upon  the  armatun;  li  of  relay  Eg,  in  aiUlition  to  the  action  of 
spring  rj.  2.  No  current.  The  armature  j  of  relay  Ej  is 
drawn  by  tlie  tension  of  spring  r^  over  against  the  contact  lever 
r,  thus  completing  the  local  circuit  of  sounderS,.  The  armature 
of  Eg  is  held  back  ly  spring  /'g,  thus  breaking  hjcal  circuit  of  Sg 
3.  Current  0/ — 3  B.  In  this  (uise  the  action  of  the  negative 
current  from  the  greater  battery  causes  the  polarized  armature 
to  press  against  the  contact  lever  r  and  overcomes  the  tension  of 
spring  g-j,  and  thus,  although  the  local  circuit  is  still  closed 
between  the  armature  j  and  contact  lever  r,  it  is  now  broken 


COMBINED  DIFKEKKXTIAIi   AND  BRIDGE   METHODS. 


821 


between  the  latter  and  the  fixed  stop  q,  and  Lence  sounder  S^ 
remains  inactive.  On  the  other  iiand,  the  negative  current  carries 
the  armature  h  of  relay  K^  to  tlie  left,  closing  the  local  circuit 
and  actuating  the  sounder  S3.  4.  Current  of —  B.  This  cur- 
rent is  not  sulfieient  to  overcome  the  tension  of  spring  q^^  and, 
therefore,  the  contact  lever  r  continues  to  rest  against  stop  q,  and 
the  local  circuit  of  Sj  is  completed.  Eelay  Rj,  which  operates 
by  negative  currents  of  any  strength,  closes  its  local  circuit 
through  the  sounder  Sg. 

In  this  arrangement  it  will  bo  seen  that  a  reversal  of  polarity 
upon  tlie  line  cannot  occur  while  a  signal  is  being  given  by 
either  key.  This  method  may  be  readily  united  with  any  suit- 
able duplex  method  to  form  a  (piadruplcx  combination. 

Fig.  147  is  a  diagram  illustrating  a  cpiadruplex:  method,  based 
upon  that  shown  in  fig.  144,  but  embodies  several  important 
modifications  and  improvements  not  shown  thera  This  arrange- 
incnc  was  extensively  employed  for  some  time  upon  the  Western 
Union  lines,  csjiecially  upon  the  longer  circuits,  and  was  ftmnd 
to  be,  in  many  res})ects,  far  superiijr  to  that  first  introduced.  It 
will  be  seen  tliat  no  changes  were  made  in  the  principle  of  the 
transmitting  ])ortion  of  the  ajiparatus,  or  the  combination  of  cur- 
rents sent  to  line  in  the  dilferent  positions  of  the  keys,  but 
portions  of  the  receiving  apparatus  were  materially  altered. 

In  fig.  147  the  polarized  relay  E^,  and  its  accompanying 
sounder,  are  placed  in  the  briilgc  5,  6,  as  before.  The  neutral 
relay,  which  was  formerly  placed  in  the  bridge  wire  also,  is 
discarded  altogether,  and  is  replaced  by  a  compound  differential 
polarized  relay  Eg.  This  is  inserted,  not  in  the  bridge  wire,  but 
in  the  line  and  earth  wires  ;  these  respectively  form  the  third  and 
fourth  sidt's  of  the  bridge,  of  which  A  and  B  are  the  lirst  and 
second  sides.  Thu.s,  when  the  resistances  A  and  B  are  made 
equal,  the  outgoing  currents  will  divide  e(|ually  between  the  line 
and  the  earth,  ami  will  neutralize  each  oth(>r  in  their  eflectupon 
the  relay  Eg.  The  latter  consists  of  two  electro-magnets  facing 
each  other,  with  a  polarized  armature  between  them.  When  no 
current  is  passing,  the  i)olarized  arinatiu'e  is  held  in  a  central 


322 


QUADRU  I'LKX   TEriE(iKAl'IIY. 


position  between  two  spring  contact  levers  N  Nj,  ami  the  cir- 
cuit of  tlic  local  relay  S  is  conij)Ieteil  tlirougli  these  and  the 
armature  lever.  The  springs  of  tlie  contact  levers  N  Nj  aro 
adjusted  with  sufficient  tension  to  prevent  tliein  from  responding 
to  the  current  of  the  small  battery  Ej  at  the  sending  station,  but 
the  additional  current  from  battery  Eg  will  overcome  the  spring 


LINE 


GROUND 


Fig.  141. 

of  N  or  of  N 1 ,  according  to  its  polarity,  and  thus  break  the  circuit 
of  the  local  relay  S,  which  by  its  back  contact  will  operate  the 
sounder  Sg.  The  electro-magnets  r  r  are  arranged  to  act  in  con- 
junction with  llg  Rg  upon  the  same  armature  lever,  and  are 
connected  with  a  condenser  c  and  a  rheostat  Xj  in  the  bridge 
•wire,  for  reasons  which  have  been  fully  explained  on  i)age  313. 


DIKKKKENTIAL   METHOD. 


323 


0  cir- 

1  tho 
,  aro 
ndirig 
n,  but 
spring 


LINE 


e  circuit 
;ratc  the 
;t  in  con- 
and  are 
e  bridge 
ige  313. 


Fig.  148  shows  the  connoction.s  of  another  form  of  (jnadniplcx 
appai'at  us,  embodying  several  important  im2)rovement.s  that  are 
not  found  in  tlie  api)ai?ituri  lieretoforc  described.  Both  receiving 
relays  |{,  and  \i.,  are  i)rovided  willidilfercntial  helices  and  polar- 
ized armatures,  and  in  general  the  dill'erential  method  is  employed 


i|i|i|ih^{i{i|i|i|i|i{i|i|i!iliF^ 


Fig.  148. 

throughout  in  place  of  the  bridge.  The  relays  Ej  and  11  j  may 
be  constructed  as  shown  in  the  figure,  or  according  to  Siemeus's 
pattern,  Exijerience  has  shown  that  the  latter  form  gives,  on 
the  whole,  the  most  satisfactory  residts,  and  it  has  therefore  been 
adopted  in  all  the  more  recent  apparatus.     The  combination  of 


824  QUADIlfI'LEX  TKl.K(iUAniY. 

tho  outgoing  cuiTciits  differs  from  that  employed  in  llic;  original 
qu:idru])l('X,  and  is  us  {(^liows: 

Kj  open  and  K^  open,  eiirrcnt  Iraversinj;  line -|-4  I^ 

K J  open  and  Kjj  closed,     "  "  '■     +     I^ 

Ki  closed  an<l  Kg  open,     "  "  "     — -iB 

K,  closed  and  K^  closed,  "  "  "     —     B 

As  ill  the  original  (piadniplcx,  key  Kj  controls  the  polarity 
of  tlio  current  going  to  line,  l)ut  the  depression  of  Kg  decreases 
the  outgoing  current,  irrespective  of  its  polarity,  from  4  B  to  B  ; 
or,  in  other  words,  (!uts  off  the  battery  3  B  'dtogether. 

The  only  matter  requiring  detailed  ex  ition  'is  the  action 
of  the  relay  Rg.     When  both  keys  arc  the  ])ositive  cur- 

rent of  both  batteries  (-f-  3  B  -j-  I^)  is  passing  over  the  line,  and 
the  polarized  armature  is  pressed  against  the  contact  lever  n^, 
which  jdelils,  thus  allowing  it  to  separate  fi'om  the  contact  lever 
n,,  and  the  circuit  of  the  sounder  Sj  is  broken.  When  Kj  is 
closed,  the  polarity  of  the  entire  battery  upon  the  line  is  reversed, 
and  the  armature  passes  over  to  the  other  side  and  presses 
against  ??3  in  the  same  manner,  so  that  tho  sounder  Sj  cannot 
be  operated  by  the  stronger  currents  of  either  polarity.  But 
the  depression  of  the  key  Kg  in  either  case  decreases  the  current, 
until  it  is  unable  to  withstiind  the  tension  of  tho  springs  of  the 
contact  levers  n^  n^,  and  thus  the  local  circuit  through  the 
sounder  Sg  is  completed,  and  the  latter  consequently  responds 
to  the  movements  of  key  Kg. 

On  circuits  exceeding  200  miles  in  length,  the  sounder  Sg 
is  preferably  o])eratcd  through  the  medium  of  a  local  relay, 
arranged  as  in  iig.  1-47.  The  combination  of  tho  outg(jing  cur- 
rents in  different  positions  of  the  keys  is  also  rearranged,  so 
as  to  conform  to  the  original  plans  (ligs.  144  and  147),  and  is 
as  follows : 

Kj  open  and  Kg  open,  cuiTcnt  traversing  line -\-      B 

Kj  open  and  Kg  closed,     "  "  "      +  4  B 

Kj  closed  and  Kg  open,     "  "  "      —      B 

Ki  closed  and  Kg  closed,  "  "  "     —  4  B 


AUUAXGKMKX'l"   OK   Al'PAKATUS   KOU   LONG   CIRCUITS.      325 


\    +       ^ 

4-4B 

—  ]i 

—  4B 


Figs.  140  luiil  150  comprise;  a  phiii  view  and  diagram  of  a 
quartette  table,  arranged  for  ([uailruplcx  working  on  a  long  cir- 
cuit, .slunving  the  relative  i)osition,s  of  the  dillcrrnt  parts  of  the 
a})panitus.  Fii  lig.  149  iIk;  conipartment  at  the  to[)  of  tlic;  figure 
is  for  receiving,  and  the  other  for  sending;  while  in  lig.  150  the 
sending  operator  occupies  the  ui)per  compartment  and  the 
receiving  operator  the  lower  one.  The  letters  and  figures  of 
reference  indicate  tlu!  same  jiarts  as  in  lig.  148.  Additional  let- 
ters of  reference  will  l)e  cxpiaineil  elsewhere.  The  main  cir- 
cuits an;  indicated  by  broken  lines,  and  the  local  circuits  by 
dotted  lines. 

In  all  of  the  methods  (tf  multiple  transmission  hitherto  known, 
■whereby  two  distinct  communications  may  bo  simultaneously 
transmitted  o\er  one  conductor  in  the  same  direction,  or  com- 
bined with  any  suitable  one  of  the  several  known  methods  of 
simultaneous  double  transmission  in  oj)posite  directions,  .so  that 
four  di.stinct  communications  may  be  transmitted  simultancou.sly, 
without  interfering  with  each  other,  it  has  been  necessary  to 
make  use  of  a  double-acting  receiving  instrument  or  relay  at  the 
receiving  station,  composeil  of  a  single  electro-magnet  having 
two  or  more  armatures,  or  else  of  two  or  more  independent 
receiving  instruments. 

The  ](racti(!al  objection  to  the  fir.st  mentioned  arrangement  is 
that  the  elTective  attracti(jn  of  the  electro-magnet  for  any  one  of 
two  or  more  armatures  is  materially  lessened  whenever  one  of  ,,, 
the  others  is  already  in  contact,  or  nearly  in  contact,  with  its 
jioles.  Thus  the  movenn-uts  of  the  scjiarate  armatures  neces- 
sarily interfere  with  each  other,  which  interference  tends  to  con- 
fu.se  the  signals.  The  second  arrangement,  viz.,  the  use  of  two 
independent  receiving  in.struments.  although  being  free  from  the 
above  mcnticjned  objections,  is  liable  to  certain  other  defects, 
the  principal  of  which  iwo  as  follows :  When  the  apparatus  is 
arranged  for  the  simultaneous  transmission  of  four  communica- 
tions, two  in  each  direction,  it  is  found  difficult  to  adjusjt  tlie 
ecpiating  resistances  and  condenser  capacities,  so  tliat  neither  of 
the  two  receiving  instruments  are  aflected  by  the  variations  in 


826 


yi  ■  ADKU I'LKX  TELEGIiAl'HV. 


KXI'I.ANATION  n|.'  KKiS.  149  AND  IM. 


K,,  Key  of  No.  1  sonilins  opcralur 

Ti,  I)()iil)li'  nirreii*.  tniiismitti^r,  opiirali'd  liy 

K,  or  /■,. 
«,,  Triiii>)rnitli'r  local,  of  tliiDc  cplln. 
A,,  Ki  y  of  No.  1  nM'i'iviiii;  operator. 
K,,  Slnifli'  iioliiri/.cd  ri'lay. 
8i,  Ucridviii','  soiindci'  opi'ratiMl  l)y  dill". 
/,,  SouniliT  local,  of  Iwn  vrUf. 
K.J,  Ki'yof  No.  ;J  fi'iiiliiiu  o|H'rnlor. 
Tj,  Sin;,'li!  I'lirri'iil   li'aii.'<iiiilti'r,  opcrali'd    l)y 

K.,  or  Aj. 
^~,  'I'raiiHmltti.'r  local,  of  three  cell!'. 


illtto. 


k\.  Ki'v  of  No.  ~'  rncoivinfr  opontor. 

U.,,  Coiiipoiiiul  pidarizc'd  relay. 

S,  Local  relay  or  repeatini;  rounder  of 

/,  liocal  of  repealini;  woiiihUt  (two  eelUi. 

S,,  Keceivini;  HiHiiKler.  operati'd  l)y  S. 

/.,.  Sounder  local,  of  Iwo  cells. 

li,  Smaller  division  of  nialn  hattery. 

■i  B,  ljar''(T  division  of  main  baltiTy. 

(i.  Switcli   for  ciiltiii!,'  out  main   liallery  and 

connectini^line toeaidi  while  halancin;;, 
X,  liarL'o  rlieost:it  for  hilancln;^  rusl stance  of 

lliiu. 


AKKAXCiEMENT  OF  AJTAUATUS  Foil  I,()XG  CIRCUIT.S. 


327 


-ti|i|i{i|i|i|i|i|iiE'i|i|i|i;i|i|i|i[— - 

ARTH  ;i;. 


F.t.l^t;JjiL 


Fhj.  150. 


y.  Klici>»tiit  fnr  compcnsalinp;  TOHiftnnrc  <if 
tmllcry  ;i  I!. 

z,  Ulii'()»tut  Tdf  conipcnsiitini;  ri-Bistimi'i"  "f 
(Mitirt,'  main  ItiiltiTV  '.\  H       It, 

f,  Kqiiiiliziri!,'  I'MiHli'riMer  placed  hutweeii  iimin 
ami  artidiiiil  liii '. 

C,  c,,  CoiulciiHrra  fur  cimincnHatin,'  sl.a'ic,  (li8- 
eliarue  from  main  line.  'I'lii!  cpiaiitity 
mul  duration  of  iliiMoniii'n«ir diHcharui' 
arc  ri'iinlali'd  li.v  niranrt  of  tlio  adjust- 
al)l«  rlicostals  rand  /■,.  'I'lic  urranur- 
went  hIiowu  ii  uiiiployi'd  only  uu  line» 


cxooodlnc:  41111  mili-H  in  Icnuiii.  Wlion  a  Btatic 
)>alani-(t  i;*  oitiaint'd.  c,  .'-lionld  Imvo  uliont 
t\\it'e  as  many  stui'tH  as  i\  (liotli  ln'inK  ad- 
jUf*tal»lt').  Tin!  condenHiT  r.^  slionld  rirroivo 
its  cliarni'  tlironuli  abont  half  tile  rt'sistancc 
rcipiirrd  lorliolli.  Kor  exainpli',  if  tlu'  nnm- 
htT  of  Hlu'cts  n^qnlnMl  in  r,  were  lio,  and  in  c^ 
mi  (total  '.KM  ami  the  ^l'si^'ta^('l'  ri'ipiired  for 
liotli  were  uMKHi  oliniH,  c,  wmild  rcipiire  l.(KHI 
and  (',  1.1)00.  OnlincHor  lesH  than  400  mileH 
the  nrranv'i'mi'nt  bUown  iu  flg.  14S  answers 
uvery  purpusu. 


328 


QIADIUI'LKX  TELEfiUAPlIV, 


the  strcngtli  or  polarity  of  the  outgoing  ciirrcut.s  ;  us  tlie  changes 
nocessarv  to  elTect  llie  jiroper  a<ljustiiicnt  or  balance  of:  one 
reL'('i\'ing  instrunK'nt  destroy  tlu;  halantu'  of  the  otlici',  and  iiiueh 
care  and  skill  are,  at  times,  recjuireil  tu  accomplish  the  desired 
result. 

Again,  when  two  receiving  instruments  are  used,  one  must 
he  snlliciently  sensitive  to  respond  reachly  to  weak  currents. 
The  other  must  be  much  less  sensitive,  responding  only  to  cur- 


rents of  greater  strengtli.  The  currenl  rei[uired  to  actuate  the 
latter  instrument  sometimes  alfecls  injuriously  tlu;  working  of 
the  more  delicate  one. 

To  nu'ct  these  dilliculties,  a  somewhat  novel  and  ingenious 
arrangement  has  been  devised,  wliich  is  shown  in  fig.  151.  Tlie 
lirinci])al  [)art  of  the  improvement  cinisists  in  llic  use  of  a  new 
form  of  double  actiug  relay,  compose  1  of  a  double  elcetro-maguet 


DOCHLK   ACTlXf!    KKLAY. 


329 


lie 


and  a  single  armature,  the  latter  capable  of  being  placed,  l)y  the 
actiim  of  the  former,  in  four  dill'ereiit  ])ositious  ccjrrespouding  to 
till!  four  possible  positions  of  the  two  kt>ys  at  the  sending  station. 
By  means  of  .suitaijly  arranged  eontactdevers,  two  iiidei)enilent 
loeal  circuits  are  Ijrouglit  into  acticjii  by  the  same  armature  in  its 
dill'ereiit  positions,  s(^  as  to  actuate  two  independent  souii'lers. 

The  diagram  shows  the  receiving  instrument  en-  relay  at  one 
terminal  station,  combined  with  other  well  known  a]H)aratus,  in 
order  to  elleet  the  simultaneous  transmission  and  reception  of 
two  communications,  in  the  same  or  in  opposite  dii'ections,  or 
i)oth,  upon  one  cimductor. 

With  the  exception  of  the  arrangement  of  contact-points  and 
thi'ir  respective  hical  connections  witli  the  levers  N  and  Xj,  and 
armature  n^,  by  means  of  which  the  latter  controls  the  local  cir- 
cuits which  oj)ci'ate  the  sounders  Sj  and  So,  tlie  construction  of 
the  receiving  instrument  is  precisely  the  same  as  that  used  in  the 
(piadruplex  system,  which  we  have  just  i;onsidered,  and  which  is 
fully  descrilteil  on  page  '''24.  As  shown  in  the  figure,  the  eon- 
tactdevers N  and  N,  ihe  receiving  instrument  turn  freely 
upon  suitable  fulcrums  at  tlieir  lower  emls,  while  tlieir  free  ii]>pcr 
(mhIs,  when  at  rest,  are  held  against  the  adjustable  contact  points 
'/ '/i  ^'y  '^'^  tension  of  the  adjustalilc  springs  r  rj.  A  contact 
point  0  is  upon  the  n{)per  extremity  of  the  contact  lc\  cr  N;  and 
ti^  is  an  insulated  sto])  occupying  a  corresponding  position  upon 
the  lever  X,.  The  contacts  q  q^  are  so  adjusted  as  to  allow  the 
arm  «j,  which  is  rigidly  attached  to  the  arinaiure  a,  to  play 
between  the  stops  o  and  Oj  ujjon  the  contact  lescrs,  Avhich  limit 
its  motion  in  each  direction,  except  at  such  times  as  the  armature 
(I  moves  with  sullicient  power  to  overcome  the  retracti!  force  of 
springs  ?•  7"j,  in  which  case  the  lever  X  or  Xj  i-  sscd  away 
from  the  contact  y  or  7 j  until  it  strikes  against  inc  adjustal'ile 
stop  p  or  ;)j. 

The  operation  of  the  two  indepenilent  transmitters  or  keys  K^ 
and  K„,  at  the  sending  station,  gives  rise  to  four  dilTerent  elec- 
trical conditions  of  the  line,  according  to  their  respective  positions 
witli  reference  to  each  other,  as  follows : 


830 


Ql'ADRUPLEX  TKI.EGRAl'IIY. 


1.  First  and  second  keys  botli  open.  Tliis  is  the  position 
of  tlie  appanitus  shown  in  tlie  fignre.  In  this  position  of  the 
keys  botli  main  batteries  are  in  eireiiit,  seiubng  to  Hnea  positive 
or  4-  cnrreiit  of  -|-  B  +  3  ]J  =  -f  4  1?. 

2.  First  key  closed  and  second  key  oiieii.  In  this  position 
both  main  batteries  are  also  in  eirenit,  sending  to  line  a  negative 
or  —  current  of  —  3  B  —  B  =  —  4  B. 

3.  Second  key  closed  and  first  key  open.  In  this  ])osition 
the  smaller  of  the  two  main  batteries  only  is  in  circuit,  sending 
to  line  a  positive  or  -(-  current  of  a  strength  of  -\-  B. 

4.  First  and  second  keys  both  closed.  In  this  position 
the  smaller  battery  only  is  in  circuit,  sending  to  line  a  negative 
or  —  current  of  a  strength  of  —  B. 

At  the  distant  terminal  of  tiie  line  L,  the  a])])aratus  is  arranged 
precisely  as  shown  in  the  lig\n'e. 

It  is  essential  that  one  sounder  (for  example,  S,)  siiould 
respond  solely  to  the  movements  of  the  key  Kj,  and  the  otiier 
snnuder,  Sj,  in  like  maimer  to  the  movements  of  the  key  Kg  ; 
while  both  should  resi)ond  when  both  keys  are  simultaneously 
depres.scd.  The  manner  in  which  this  result  is  accomplished 
will  be  understood  by  the  following  explanation  of  the  elTect  of 
each  of  the  above  meiition(Hl  electrical  conditions  of  the  line 
upon  the  receiving  instrument. 

1.  Positive  current  from  both  batteries  (-(-  4  B).  The  local 
circuit  of  sounder  Sj  is  open  between  the  })oint  o  and  arm 
Oj,  and  that  of  Sg  between  the  lever  Nj  and  the  stop  q^, 
because  the  action  of  the  current  upon  the  anuature  a,  teuding 
to  attract  it  toward  yi , ,  is  strong  enough  to  ()V(>rcome  the  tension 
of  the  spring  r^,  and  force  the  lever  Nj  against  the  stop  p^. 

2.  Negative  cui'rents  from  both  batteries  ( — ■  4  B).  The 
local  circuit  of  soumler  S,  is  closed  at  the  point  of  contact 
between  arm  (t^  iind  contact  lever  N  ;  but  that  of  sounder  Sj  is 
broken  betwe(>ii  tl,  contact  levcir  X  ami  the  stop  7,  because  the 
strength  of  the  eurreut  upon  the  lino  is  so  great  as  to  overcome 
the  tension  of  th  spring  r,  and  force  the  lover  N  against  the 
stop  2'- 


1 


DOUBLE   ACTING   RELAY. 


331 


aed 


3.  Positive  current  from  battery  15  only  (-)-  B).  Tlie  local 
circuit  of  sounder  Sj  is  broken  between  tlie  arm  rtj  and  the  con- 
tact o  on  the  lever  N,  but  that  of  sounder  Sg  remains  closed, 
because  the  power  of  the  current  upon  tlie  line,  though  sufficient 
to  move  the  arm  Oj  away  from  the  stop  o,  is  not  able  to  overcome 
thespring  i\,  and  separate  the  lever  Nj  from  the  stoj)  q^. 

4.  Negative  current  from  battery  B  only  ( — B).  Tlie  local 
circuits  of  both  sounders  Sj  and  Sg  remain  closed,  because 
the  strength  of  this  current  is  sufficient  to  bring  the  arm  a^  into 
contact  with  the  stop  o  upon  the  contact  lever  N,  but  is  not 
enough  to  overcome  the  spring  r,  and  thus  separate  the  lever  N 
from  the  stop  q. 

Thus  it  will  be  understood  that  the  armature  a  is  caused  to 
assume  four  different  positions  corresponding  to  the  four  different 
electrical  conditions  of  the  line. 

When  the  armature  is  in  either  of  its  extreme  positions  the 
local  circuit  of  the  sounder  Sg  is  broken.  When  the  armature 
passes  directly  over  from  one  extreme  position  to  the  otlier,  it,  of 
course,  closes  the  local  circuit  for  an  instant  as  it  ])asses  the 
middle  point,  but  not  long  enough  to  produce  any  effect  whatever 
upon  the  sounder  Sj,  whicli  remains  inactive. 

Condensers  Cj  and  Cg  are  connected  to  the  artificial  line  A  for 
the  purpose  of  compensating  the  static^  di.schargc  .)f  the  line. 
Tlie  adjustable  rheostats  Vj  and  Y .,  are  used  in  order  to  regu- 
late the  action  of  the  condensers  and  render  their  charge  and 
discharge  nearer  the  same  duration  as  that  of  the  line. 

An  independent  condenser  C  is  arranged  with  one  set  of  its 
poles  in  connection  with  the  main  line  L,  and  the  other  set  with 
the  artificial  line  A. 

No  effect  is  produced  upon  this  condenser  by  the  outgoing 
current,  as  tlie  potential  oC  the  latter  is  substantially  the  same 
on  each  side. 

The  incoming  current  from  the  distant  station,  meeting  with 
the  resistance  of  tlu;  helices  M  Mj,  flows  into  and  charges  the 
condenser,  whicli  remains  charged  until  a  reviTsal  of  tlie  current 
tiikes  place  upon  the  line,  when  it  instantly  disciiarges  itself  and 


3;i2 


QUADRUPLEX  TELEGRAl'IIY. 


sends  a  niomentavv  juilsation  throiigli  tlio  electro-magnets  M  M^, 
thus  tending  to  liastt'ii  the  action  of  tlic  receiving  magnet  ujion 
its  armature  at  each  I'eversal,  thereby  improving  the  signals  upon 
long  lines. 

Tlic  eflcctive  action  of  this  condenser  may  be  much  increased 
if  desired,  by  augmenting  tiie  resistance  of  tlie  helices  M  Mj, 
or  by  inserting  additional  resistances  between  thest;  and  the 
jimetion  of  the  wires  leading  to  the  condenser  on  each  side. 

The  double  acting  receiving  in.strument  here  described,  and 
shown  in  the  figure,  is  equally  serviceable  in  connection  with  the 
arrangement  of  main  batteries  illustrateil  arul  described  on  pages 
314  and  318. 

The  apparatus  has  been  tested  in  practical  service  ujxm  all  of 
the  longest  circuits  on  which  the  (piadruplex  system  is  worked 
from  the  Western  Union  'I'elegraph  Cum|)any's  Xew  York  olRce, 
and  continued  in  constant  use  for  one  week  on  the  New  York 
and  Albany  circuit  with  very  satisfactory  results.  In  i-egular 
practice,  however,  it  has  been  found  preferable  to  use  two  inde- 
pendent relays,  thus  enabling  each  opei-ator  to  adjust  his  own 
instrument. 

On  l'"ebruary  7,  1877,  a  tost  was  made  on  a  direct  circuit 
lietwecn  Xew  York  and  (Jhieago,  via  Pittsi)urgh,  Pa.,  a  (lis 
tancc  of  itl3  miles,  and  the  simultaneous  reception  of  two  com- 
munications in  tlie  .same  direction  was  accomplished  at  a  s]i(>ed 
of  thirty  words  a  minute  on  each  of  the  respective  sounders  Sj 
and  Sg. 

Fig.  152  shows  a  general  plan  of  the  quadruplex  apparatus 
now  in  u.se  on  the  lines  of  the  Westiuni  Union  Telegraph  Com- 
pany, and  which  embodies  the  more  recent  improvement.s. 

The  transmitting  devices,  both  in  construction  and  moch;  of 
operation,  are  jireeiscly  similar  to  those  referred  to  in  connection 
with  lig.  151,  so  that  it  will  be  necessary  here  to  refer  onlv  to  the 
effect  produced  by  the  o])eration  of  the  two  indei)endent  transnnt- 
ters  or  keys,  which  is  as  follows: 

1.  Key  K^  and  K„  both  open,  in  this  position  the  entire 
batterv  is  in  circuit,  sending  to  the  liiu;  a  netrative  or  —  current 


of_B  — 3B: 


-4B. 


JMI'HOVEI)   JiKLAV.  666 

2.  Key  K^  r.pcii  uihI  K^  closed.  la  tliis  cast;  liaUery  B 
only  is  in  circuit,  sendin.ix  to  tlic  lino  a  nogativf  oi'^ — current  of 
—  B. 

3.  Key  Ki  closeil  and  Kg  oiten.  The  entin;  battery  is  again 
in  circuit,  but  in  this  case  with  the  positive  or  -f-  pole  to  the 
line,  sending  a  current  of  -)-  3  B  +  B  =  -j-  4  ]i. 

4.  Key  K^  and  Kg  both  closcil.     In  this  position  the  battery 

-  ' v«. 


Bonly  is  in  circuit,  sending  to  the  lino  a  ])ositive  or  4"  current 
of  +  B. 

Thus  it  will  be  understood  that  the  line  is  caused  to  assume 
loiu-  distinct  electrical  conditions,  corresponding  with  the  four 
possible  positions  of  the  keys  at  the  transmitting  station. 

The  receiving  apparatus  consists  of  two  sounders,  Sj  and  Sg, 
which  are  controlled  by  rekys  11 1  and  R.,.  The  construction  of  R^ 


884 


QL'ADRUPLEX   TELEGRAPHY. 


is  tlic  sumo  in  every  particular  as  that  lierctofoj-e  described  ;  it 
being,  in  fact,  simply  a  i)olarized  relay  capable  of  responding  to 
positive  anrl  negative  currents. 

"J'lie  relay  Kg,  however,  differs  materially  from  relay  R^  in  the 
arrangement  of  its  local  circuit  connections,  by  means  of  which 
the  sounder  Sg  is  ojierated  ;  and  the  improv(;mentu[)on  the  form 
of  relay  heretofore  vised  consists  cliiefly  in  dispensing  with  one 
of  the  sujtplementary  contact  levers,  whereby  the  ap])aratus  is 
not  only  simplified,  but  made  to  work  with  greater  facility  and. 
certainty  through  long  circuits. 

The  noi'mal  pf)sition  of  the  apparatus,  wlien  neither  key  at  the 
transmitting  station  is  de[)r('ssed,  is  tiiat  shown  in  the  diagram. 

The  manner  in  which  tlie  relays  llj  and  Rg  operate  in  each 
of  the  four  electrical  conditions  of  the  hue  mentioned,  so  as  to 
cause  he  sounder  Sj  to  res]K)nd  solely  to  the  movements  of  key 
Kj,  and  the  sounder  Sg  in  like  manner  to  the  movements  of  key 
Kj,  and  both  in  response  to  a  simultaneous  depres.sion  of  keys 
Kj  and  Kg,  will  be  understood  by  reference  to  the  following 
explanation : 

1.  Kj  and  Kg  both  ojien.  A  negative  or  —  current  from 
both  batteries  ( — 4  B).  The  local  circuit  of  sounder  S^  is  kept 
open,  becau.sc  the  ])olarity  of  the  line  current  tends  to  hold  the 
armature  h  of  relay  llj,  on  its  back  stop  p.  The  local  circuit 
of  sounder  .Sg  is  also  open  between  armature  _;'  and  lever  r, 
because  the  current  on  the  line  is  sufTicicutly  ])owerful  to  over- 
come the  spring  r^,  and  hold  armature  j  against  stop  o ;  thus 
sounder  Sg  remains  inactive. 

2.  Kj  open  and  Kg  closed.  A  negative  or  —  current  from 
battery  B  only  ( —  B).  The  local  circuit  of  sounder  Sj  re- 
mains oi)cn  between  stop  Pj  and  armature  A,  because  the 
polarity  of  the  curr(!nt  is  such  as  to  hold  the  latter  against  stop 
p.  The  action  of  thisearrcnt  upon  relay  R,  is  to  cause  its  arma- 
ture y,  assisted  by  spring  i\,  to  move  to  the  left  and  make  con- 
tact with  the  lever  r,  but  not  with  sufTicicnt  force  to  overcome 
the  retractile  spring  ^j,  thus  leaving  armature  /  in  a  central 
position  between  stoj)s  o  and  Oj,  thereby  closing  the  local  circuit 
and  operating  sounder  Sj. 


IMPROVED   IJELAY. 


885 


3.  K,  closed  imd  K„  o|1(mi.  A  jiositivc  or  +  current  from 
both  batteries  (+  -t  B).  This  current  causes  the  armature  h 
uf  relay  Rj  to  move  to  the  left,  thus  closiug  the  local  circuit  at 
stop^jj  and  actuating  .sounder  S,.  The  armature,/ of  relay  R3 
is  also  strongly  attracted  toward  the  left,  ])ressing  against  the 
yieliliug  lever  r  with  suflicient  force  to  overcome  tiie  sj)ring  y,, 
and  press  the  former  against  the  stop  Oj,  thus  opening  the  local 
circuit  of  vsounder  Sg. 

4.  Keys  Kj  and  Kg  I'Otli  closed.  Positive  or  -(-  current 
from  battery  B only  (-|-  B).  Kelay  Ilj,  which  is  ;iri-anged  to  close 
its  local  circuit  by  positive  currents  of  any  strength,  actuates 
the  sounder  S^  precisely  as  in  the  third  case.  'J'hc  current  upon 
the  line  in  this  case  is  not  of  sufficient  strength  to  hold  the 
armature  /  of  relay  Rj  against  sto})Oj;  con.sefpiently  it  moves, 
together  with  lever  r,  assisted  by  spring  q^,  to  a  central  jDosition, 
thus  closing  the  local  circuit  between  armature  /  and  stoj)  q 
through  lever  ?•,  thereby  operating  sounder  S^.  When  the  arma- 
ture y  of  relay  Rj  passes  directly  over  from  one  extreme  ])osition 
to  the  other:  foi'  example,  from  stop  0  to  Oj,  it  will  be  observed 
that  the  local  circuit  is  closed  for  an  instant,  but  not  long  enough 
to  produce  any  effect  wliatever  upon  the  lever  of  sounder  Sg. 

It  is  therefore  obvious  that,  with  the  apparatus  as  arranged 
above,  two  conunuuications  may  be  simultaneously  transmitted 
over  a  single  conductor,  and  the  signals  recorded  with  facility 
and  accuracy. 

In  order  that  four  communications  may  be  made  to  pass 
simultaneously  over  a  single  conductor,  it  is  oidy  necessary  to 
(•ombine  the  apparatus  here  described  with  any  out;  of  the  several 
known  methods  of  simultaneous  transmission  in  opposite  direc- 
tions. The  arrangement  in  general  use  for  the  accompli.shment 
of  this  pui'pose  upon  the  Western  Union  Telegraph  Company's 
lines  is  that  known  as  tlie  differential  metiiod.  A  system  of 
du})lex  telegraphy  known  as  the  bridge  method  may  be  used 
instead  of  the  diflferential.  or,  instead  of  cither  of  these,  a  com- 
bination of  the  differential  and  bridge  methods.  In  practice  the 
latter  lias  been  found  preferable,  more  especially  on  the  longer 


33t) 


QL'AUULU'LKX   TELKGUAl'lIY. 


circuits,  where  the  sifjnals  have  tu  Ix^  rctransmittod  nutnmatically 
over  ail  adjniiiing  circuit,  in  whicli  case  it  is  ahsoiutclv  essential 
that  tlic  signals  sliouUl  Ijc  reeonlod  ])crl'ectly  at  the  repeater 
station. 

Tlu'  last  nanieil  ]>hiii  is  in  operatii)n  on  tiio  New  Voiic  and 
Chicago  (inadrnplex  circuit,  an^anged  so  tliat  signids  I'roiii  New 
York  and  Chicago  are  at  Bullalo  autoinatically  retransmitted  in 
either  direction.  Before  considering  the  arrangement  for  repeat- 
ing from  one  circuit  into  anotlier,  liowever,  it  will  lirst  he  well 
to  describe  the  difTerent  instruments  more  in  detail  than  we  have 
yet  done.  A  few  words  also  regarding  the  setting  up  and 
adjustment  of  the  ap2)aratus  will  not  be  out  of  place  here. 


DIKECTIONS   FOR  SETTIN(;   VV  TllK  Ql'ADRUPLEX. 

The  diagram,  figs.  149  and  150,  will  sufliciently  explain  the 
manner  in  which  tiie  instrument  should  be  sot  up  and  connected 

The  smaller  section  of  the  batteiy  B  usually  contains  about 
one  third  the  number  of  cells  that  the  larger  section  8  B  docs. 
The  rheo.stat  z  should  be  as  nearly  as  ]iossible  etiual  to  the 
internal  resistance  of  (B-|- •^>  B)  =4  B.  The  resistance  of  y 
should  be  e(|ual  to  the  internal  resistance  of  th(>  portion  3  B  of 
the  battery. 

TIIK   WOUBI.E   CURRENT    TUAXSMITTEK. 

This  is  represented  at  T^  in  figs.  148,  149  and  150,  and  is 
operated  by  the  key  K^  and  a  local  Ijattery  e^,  usually  of  three 
cells.  The  double  current  transmitter  is  sometimes  construc'Lou 
as  shown  in  lig.  153,  but  a  simpler  and  far  better  arrangement  has 
been  recently  introduced,  which  is  shown  in  lig.  154.  The  draw- 
ing is  an  end  view  of  the  transmitter,  and  shows  the  pole  ehan'nnE 
apparatus  distinctly.  The  adjustable  contact  screws  a  and  a, 
are  supported  by  and  are  in  electrical  connection  with  the  post 
P,  wliich  is  in  turn  connected  with  the  line  wire.  The  post  also 
supports  two  contact  sjirings  Sj  and  Sj,  which  are  insulated  from 
it  and  connected  by  wires  1  and  12  with  the  ziijc  and  copper 


DOUBLE  CURRENT  TRANSMIITKR. 


887 


poles  of  tlio  miiin  battery,  respectively.     The  lever  l^  of    tlie 
transmitter  is  connected  with  the  earth. 

Tb&  proper  adjustment  of  this  transmitter  is  a  matter  of  the 


Fig.  153. 

greatest  importance  to  ensure  the  succe.ssful  working  of    the 
apparatus.     In  order  that  it  may  follow  the  movements  of  the 

a 


key  with  promptness,  the  play  of  the  lever  t^  between  its  limit- 
ing stops  near  tlie  electro- magnet  .should  not  exceed  ^\  of  an 
inch.     The  contact  screws  must  be  so  adjusted  that  at  a  point 


888 


QUADRUPLEX   TELEGRAPHY. 


about  midway  of  the  stroke  of  the  lover  t^  the  springs  S  and  S, 
will  i)otli  1)0  ill  t'oiituct  with  it  at  the  same  time,  Imt  for  the 
shortest  possible  period.  The  easiest  way  is  to  lirst  temporarily 
adjust  the  upper  limiting  stop  at  the  opposite  eud  of  the  trans- 
mitter lever  (^,  so  as  to  reduee  th(>  play  of  the  level  lo  ^^  of  an 
ineh.  or  about  half  the  ordinary  distauee  allowed  for  a  sounder. 
Then  gradually  raise  the  eontaet  serew  a  until  the  spring  Sj 
l)arely  touches  the  l(>ver  l^,  being  careful  to  move  the  screw  no 
further  than  is  necessary  to  do  this.  Then  liwer  the  eontaet 
serew  a,,  and  adjust  the  spring  Sj  in  the  same  way.  Finally, 
raise  tlu;  limiting  stop  at  the  other  end  of  the  lever,  so  as  to  give 
it  the  usual  play  of  about  tjV  "'^  aninch.  In  its  vibration  the 
lever  t^  should  touch  one  of  the  sprinjxs  S,  or  Sg  a:  the  same 
instant  that  it  leaves  the  other.  If  the  springs  are  ''/''■  steil  too 
far  apart  there  will  be  a  break  in  the  circuit,  as  the  lever  will 
break  contact  with  one  spring  before  it  touches  the  other.;  if  too 
Ti(Uir  together,  the  battery  will  bo  plac(Hl  on  short  cinMiit  too 
long,  from  one  eontaet  being  made  before  the  oIIkm*  is  broken. 
By  careful  adjustment  this  period  can  be  rednecd  to  almost 
nothing,  and  the  more  accunato  this  adju.stment  the  better  will 
be  th(>  pei-formance  of  the  apparatus. 

TIIK  SINGLE  CURUIC.VT   TR.VN'SMITTEK. 

This  is  similar  to  the  transmitter  of  the  Stearns  duplex.  The 
play  of  the  lever  of  the  transmitter  should  be  about  ^ig-  of  an 
inch  between  the  limiting  stops  and  the  contact  screw  A,  lig.  155, 
adjusted  so  that  when  the  key  is  closed  and  the  transmitter  in 
the  ]iosition  represented,  the  spring  B  will  be  slightly  separated 
from  the  contact  point  on  the  end  of  the  lever  D. 


<^':;# 


THE  CO.HPOUND   POLARIZKD   RELAY. 

This  relay  is  r(>proseiitcd  by  Rj,  in  ligs.  148  and  149,  and  the, 
sounder  connected  with  it  responds  to  the  signals  given  by  tlu; 
doul)le  current  tnmsmitter  at  the  sending  station.     The   relay 
consists  of  four  separate  electro-magnets,  arranged,  in  pair.s,  with 
their  poles  facing  each  other,  upon  opjjositc  sides  of  a  double 


SINGLE   I'L'KUENT  TKANaMlTTJiK. 


339 


j)olarizc(l  armature.  The  connections  and  principle  oC  operation 
have  already  been  explaiued  in  foniieetioii  with  lig.  148.  Tlw 
proper  adjustment  of  the  annatui-cs  luul  local  eontaet  levers  of 
this  relay  i'*  a  matter  of  much  inijiortancc.  and  the  following 
directions  should  be  carefully  observed  : 

b'i".  150  is  a  perspective  view  (jf  the  coni])(>\ind  rehiy,  showing 
the  contact  levers  and  their  adjustment.  The  electro-magnets 
M  M  should  be  adjusted  by  means  of  the  check  nuts  at  the 
back,  so  that  their  jioU's  are  at  etpial  distances  from  the  opposite 
faces  of  tl-.e  polarized  armature  a.    Tlie  play  of  the  armature  lever 


Fig.  155. 

is  regulated  by  the  screw  stops  pg  and  p4,  which  limit  the  move- 
ments of  the  contact  levers  NN,  in  one  direction,  while  the 
stops  pj  and  pg  limit  them  in  tiie  other  direction.  To  adjust 
these  levers,  the  screws  p^  and  p^  should  be  withdrawn  until  tho 
contact  points  upon  the  armature  lover  a  are  touched  by  those 
upon  the  levers  N  N,  upon  each  side,  so  th.nt  tho  loc.^1  circuit 
can  pass  through  tho  lover  from  N  to  N,  whm  the  armatures  is 
in  a  middle  position,  but  will  bo  intorrui-itod  by  its  slightest 
movement  in  either  direction.  The  play  allowed  to  the  contact 
levers  by  the  stops  ^3  and  p^  may  be,  with  advantage,  consider- 


840 


QUADRL'PLKX  TBLEGRAPIIY. 


ably  less  tlian  than  that  of  an  ordinary  relay.  The  proper  ten- 
sion of  the  s^jriuys  ?i  and  n  ^  depends  upon  the  condition  of  the 
line  current,  and  will  be  referred  to  hereafter. 


THK  SINGLE  POLARIZED  RFJ.AY. 

Tliia  is  shown  at  R,,  in  fips.  147,  148  and  150,  and  is  simply 
a  Siemens  polarized  relay,  which  should  hcidjustcd  with  a  play 
about  the  same  as  that  of  the  ordinary  Morse  relay.    This  may 


ADJUSTMENT   OF   THE   yL'ADliUl'LEX 


S41 


ir  ten- 
jf  the 


be,  and  usually  is,  constructed  in  the  same  form  as  lig.  156,  l)ut 
without  movable  contact  levers  N  Xj. 


is  simply 
th  a  play 
rhis  may 


ADJUSTMENT   OK  TIIK   AI'I'AKATUS   F(Mi  WOKKINti. 

The  said  an*angements  liaving  been  properly  i.iaile  at  both 
stations,  one  station,  which  for  convenience  we  will  call  station 
A,  commences  by  sending  signals  from  the  i)ole  ciianging  traas- 
mitter  1\,  having  been  careful  to  leave  key  Kg  or  k^  of  trans- 
mitter Tj  open.  Station  B  then  signals  to  station  A  in  the  came 
manner,  which  signals  will  be  received  upon  the  polarized  relay  II. 
If  the  signals  come  reversed,  or  on  the  back  stroke,  the  direc- 
tion of  the  incoming  current  through  the  relay  must  be  reversed. 
Station  A  next  instructs  B  to  gnjuiid.  B  complies  by  turning 
the  urtu  of  the  switch  Q  (lig.  149)  from  q^  to  ([^^  which  sends 
the  incoming  current  direct  to  the  eartli  dirough  the  rcsistanci^  Z, 
which  has  already  b^^.i  .  '  ^'sted  to  equal  that  of  the  entire  bat- 
I  tery  (^Kj  -)- I'^j)-     Station  '\.  lusn  grounds  by  placing  his  own 

switch  in  tiie  same  jicsition,  ind  adjusts  his  polarized  relay  Rj, 
so  tiiat  the  armuf.ure  will  remain  at  rest  indifferently  upon  cither 
its  front  or  back  contact  stop,  when  placed  l)y  the  finger.  Next, 
station  A  closes  the  single  current  transmitter  Tg  by  means  of 
Kg  or  /cg  ;  turns  the  switch  Q  back  to  its  original  position,  that 
is,  to  the  left,  sending  the  entire  battery  to  line.  Tin-  resistance 
X  (lig.  150)  .should  now  be  altered,  until  the  armature  of  the 
polarized  relay  Rj  remains  indifferently  on  either  side  when 
l)laeed  by  the  linger  as  before.  When  this  is  accompli.shed,  the 
line  resistance  a",d  rheostat  resistance  in  X  will  be  equal. 

To  ol)tain  the  "lectro-stalic  balance,  station  A  transmits  iloLs 
or  dashes  by  nieai  <  of  transmitter  Tj,  ;inrl  at  the  same  time 
alters  the  caj)acity  of  the  condenser  c^  Cg  (lig.  149),  until  it 
neutnalizes  the;  discharge  wiiieh  takes  place  at  the  end  of  each 
signal,  and  is  manifesteil  u])oii  the  relay  lip  The  electro-static 
bahuK'C  of  this  relay  insures  that  of  relay  Rj  without  further 
])rec;autioii.  Finally,  station  A  again  turns  switeh  Q  to  the 
right,   upon  point    7.,.   and  station.   15    now   jirocecds  to  obtain 


342 


QUADRUl'LEX   TELEGKAl'HY. 


<i  T)alance  in  the  same  way.  Having  aceoinplished  this,  lie 
notifies  A. 

Station  B  is  then  requested  to  send  from  transmitter  '\\,  leav- 
ing T3  open  or  at  rest.  Tlie  signals  are  received  at  A  on  relay 
Bj,  and  at  the  same  time  the  springs  n  n^  (fig.  156)  of  the  com- 
pound relay  Kj  should  be  ])ulled  nj)  sufficiently  to  hold  the 
armature  a  at  rest  in  a  central  position,  with  the  local  relay  or 
rejjeatiiig  sounder  S  (lig.  140)  closed.  Next,  15  is  rei|uested  to 
leave  transmitter  Tj  at  rest  and  send  signals  on  Tj.  These  sig- 
nals should  be  received  at  A  upon  the  ctJinpound  relay  II2  only. 
With  currents  of  one  polarity  the  armature  a  will  move  to  the 
left,  aad  with  currents  of  the  other  polai'ity  to  the  right,  but  in 
either  case  it  should  operate  the  sounder  Sg  by  means  of  the 
local  relay  S.  When  the  armature  ]>asse.'3  from  one  extreme 
jiosition  to  the  other  by  a  change  of  polarity  upon  the  line,  the 
relay  should  not  give  a  false  dot  as  it  pas.ses  the  central  position. 
The  contact  ])oints  of  the  local  relay  or  repeating  sounder  S 
should  be  adjusted  as  close  as  those  of  an  onlinary  relay. 

The  above  described  apparatus  is  suitable  for  use  upon  lines 
from  800  to  600  miles  in  length.  For  lines  under  BOO  miles  in 
length,  the  modification  of  the  apparatus,  shown  in  fig.  148,  and 
which  is  of  .somewhat  simpler  construction,  is  usually  employed. 

Simvdtaneoiis  transmission  in  ojiposite  directions,  at  the  rate 
f)f  fifty-eight  words  per  minute  each  way,  is  now  carried  on  be- 
tween New  York  and  Washington,  by  the  apjilicatiou  of  this 
quadruplex  method  to  the  Phel|)s  ele(;tro-motor  ])rinter.  This 
leaves  two  sides  free  for  exchanging  service  signals,  or  for 
carrying  on  two  .separate  communications  by  the  Morse  appa- 
ratus. 

The  arrangement  for  repeating  from  ou(!  ([uadruplex  circuit 
into  another  is  very  simple  in  principle,  and  consists  in  ])lacing 
the  two  tran.smitters  of  one  line  in  the  same  local  circuits  with 
the  corresponding  receiving  sounders  of  the  other  line.  The 
dctivils  are  more  fully  dcsci'ibcd  on  page  355.  By  this  arrange- 
ment New  York  is  enabled  to  carry  on  four  di.stinct  communi- 
cations simultaneously  with  St.  Louis,  a  distance  of  about  1,100 


ADJUSTMENT   OK   THK   g Lf ADKUPLEX. 


343 


he 


-^l[lt*-t4llf*---f 


"OO 


I3> 


344 


QUADRUPLEX  TELEGRAPHY. 


miles,  by  means  of  a  quadruplex  repeater  at  Pittsburg  ;  and  witH 
Chieago,  1,000  miles,  by  means  of  a  repeater  iit  Buffalo. 

Although  the  quadruplex  lias,  in  a  great  measure,  taken  the 
place  of  the  duplex  upon  many  of  the  lines  between  the  more 
important  telegraphic  centres,  the  latter  system  is,  nevertheless, 
still  em})loyed  to  a  considerable  extent  between  points  of  less 
importance  whore  the  business  is  not  sufficient  to  keep  the 
quadruplex  constantly  employed;  and  in  numerous  cases  it 
forms,  in  connection  with  this  system,  both  a  convenient  and 
valuable  auxiliary  for  supplying  direct  communication  between 
several  different  stations  at  one  and  the  saine  time. 

There  are  various  ways  in  which  these  two  systems  may  be 
combined  so  as  to  meet  the  numerous  requirements  of  the  ser- 
vice;, but  it  will  be  necessary  to  describe  and  illustrate  here  only 
such  as  are  now  in  actual  operation  and  by  experience  have  been 
found  serviceabl(\ 

A  ))lan  of  the  apparatus  as  arranged  at  repeating  station,  form- 
ing the  common  terminus  of  one  quadrujilex  and  two  duplex  cir- 
cuits, is  shown  in  fig.  157.  By  this  combination  two  independent 
communications  passing  in  the  same  direction  over  the  quadru- 
plex circuit  may  be  automatically  retransmitted  from  the  i^epeat- 
ing  station  over  two  separate  and  independent  duplex  circuits 
extending  to  dilTcrent  points,  wlille  at  the  same  time  two  com- 
munications passing  in  the  opposite  direction  over  the  duplex 
circuits  may  be  repeated  into  and  over  the  quadruplex  circuit. 

For  convenience  of  explanation  we  will  take  an  actual  case,  and 
suppose  the  repeating  apparatus  to  be  pla<;cd  at  Bos^ton,  which  is 
in  connection  with  New  York,  240  miles  distant,  by  quadruplex, 
and  with  Duxbury  and  St.  John,  respectively  40  and  469  miles 
di.^Jtant  by  dujtlex. 

In  order  to  effect  the  desired  retransmission  of  the  different 
sets  of  signals  passing  through  the  apparatus,  it  is  necessary  to 
form  separate  connections  between  the  several  receiving  instru- 
ments ami  the  transmitters  of  the  different  lines  into  which  the 
signals  are  to  be  repeated. 

This  is  done  by  means  of  the  local  circuits,  in  a  manner  wiiich 
will  now  be  explained. 


'• 


COMBINED   QUADRUPLEX   AND   DUPLEX   CIRCUITS. 


345 


iittou  Wo  connects  tlie 
local  circuit  of  Rg  in  line  L  with  that  of  the  transmitter  t^  in 


As  ordinarily  arranged  for  single  circuit  working,  the  relay  Rj 
(fig.  167)  of  the  New  Yoric  line  L,  operates  the  sounder  Sj  by 
means  of  the  local  battery  Bj ;  and  key  k^,t\\e  transmitter  t^,  of  the 
Duxbury  line  L^  by  means  of  the  local  Cj.  For  direct  through 
working,  however,  and  in  order  that  the  received  New  York 
•signals  may  be  communicated  fronitlu;  relay  Rj  to  the  transmit- 
ter <j,  and  thus  be  repeated  into  the  Du.xbury  line,  a  switch  or 
button  IV  ^  is  so  arranged  that  it  forms,  when  closed,  a  part  of 
each  of  the  two  separate  local  circuits  containing  the  relay  R^  and 
the  transmittci  i^,  l)ut  when  open  throws  the  two  circuits  into 
one,  so  that  relay  Rj  operates  the  transmitter  t^  as  well  as  the 
sounder  Sj. 

In  a  similar  manner  the  circuit,  including  sounder  5j  of  lino  Lj 
is  combineil  with  that  containing  the  transmitter  Tj  of  line  L, 
by  means  of  the  button  Wj,  whiU;  the 
local  circuit  of  Rg  in 
the  St.  John's  line  Lg. 

Anoth(!r  button  w^  in  lik(!  manner  also  connectvS  the  local 
circuit  of  relay  r^  in  line  Tjj  with  that  containing  the  transmitter 
Tj  of  line  L. 

When,  therefore,  the  buttons  W,  Wg,  u\  and  w.^  are  all 
clo-sed,  the  three  main  lines  L,  Lj  and  Lg  may  l)e  operated  inde- 
pendently ;  the  New  York  line  as  a  quadru[)lo.x  and  the  Duxbury 
and  St.  .Tohn's  lines  as  separate  duplex  circuits. 

When,  on  the  other  hand,  the  buttons  are  all  open  and  the 
switches  of  keys  Kj  Kg,  Ic^  k^  closed.  New  York  is  able  to 
transmit  simultaneously  two  independent  communications  over 
the  line  L  to  Boston,  where  one  of  them  will  then  be  automati- 
cally retransmitted  by  the  relay  Ri  and  transmitter  t^  over  line 
L,  to  Duxbury,  and  the  other  by  relay  Rg  and  transmitter  f^ 
over  line  Lg  to  St.  John's.  While  this  is  being  done  Duxbury 
and  St,  John's  may  also  send  communieations  simultaneously 
over  lines  L,  and  Lg  respectively  to  Bost<m,  where  relays  r,  and 
j-g  will  then  repeat  them  into  line  L  and  to  New  York.  It  will 
thus  be  seen  that  New  ^'ork  has  jiractieally  sejiarate  duplex 
circuits  to  Duxbury  and  St.  John's,  and  that  any  or  all  of  the 
corrcs[)ondeiice  may  be  read  at  l?oston. 


346 


QUADRUPLEX  TELEGRAPHY. 


By  properly  arranging  the  buttons  Wj  AVg'  ^i  ^"^^  ^''21  cither 
lino  of  communication  may  be  worlced  through  direct  oi-  be 
divided  at  Boston  without  reference  to  what  is  being  done  on  the 
other.  The  manner  of  effecting  this  will  be  sufficiently  obvious 
without  further  explanation. 

We  have  thus  far  considered  that  the  signals  transmitted  from 
New  York  and  retransmitted  at  Boston  into  line  Lg  were  copied 
at  St  John's,  N.  B.  It  is  proper  to  state,  however,  that  in  prac- 
tice New  York  and  North  Sydney,  C.  B.,  work  the  line  together 
duplex,  a  distance  of  1,159  miles,  by  means  of  a  second  duplex 
apparatus  at  St.  John's,  constituting  with  the  first  a  duplex 
repeater. 

A  modification  of  the  plan  shown  in  fig.  157,  and  just 
described,  has  developed  a  much  wider  field  for  i)ractical  opera- 
tion. This  consists  in  dispensing  with  one  duplex  circuit. 
Thus,  for  example,  if  the  Duxbury  line  Lj,  and  the  apparatus 
connected  therewith  be  removed,  it  will  readily  be  undei-stood, 
fronr  what  wc  have  already  said,  that  New  York  and  North 
Sydney  would  still  be  able  to  work  duplex,  while,  at  the  same 
time  also.  New  York  and  Boston  could  work  duplex  together 
without  regard  to  what  is  passing  between  tlu;  two  former. 

Before  describing  the  manner  of  working  the  quadruplex  in 
connection  with  the  contraplex  or  diplex  .systems,  it  will  first  be 
well  to  devote  a  few  words  to  the  consideration  of  these  systems 
alone. 

The  terms  contraplex  and  diplex  are  here  applied  as  .specific 
names  for  designating  clearly  the  way  in  which  the  particular 
simultaneous  double  transmission  to  which  we  wish  to  refer  is  ef- 
fected. Thus,  for  instance,  two  messages  may  be  sent  over  a  single 
wire  in  the  same  or  in  opposite  directions,  and  when  we  do  not  care 
to  particularize  cither,  we  simply  allude  to  them  under  the  moro 
common  generic  name  of  duplex  transmission,  which  includes 
both.  "When,  however,  wo  wi.sh  to  speak  of  either  method  l)y 
itself,  we  use  the  term  diplex  for  simultaneous  transmission  in 
the  same  direction,  and  contraplex  for  that  in  opposite  direction.s. 
As  these  terms  are  not  in  very  general  use,  this  explanation  here 
will  not  be  out  of  place. 


AKKAXGEMEXT   FOK   CONTKAPLEX  THAXSMISSIOX. 


347 


Figs.  158  unci  159  show  the  application  of  a  contraplex  sys- 
tem, in  whicli  one  set  of  signals  are  made  hy  a  series  of  changes 
in  the  polarity  of  the  current,  and  the  other  l)y  changes  in  itA 
strength. 

In  fig.  158,  <i  is  the  lever  of  a  double  current,  or  i)ole  chang- 
ing transmitter,  which  is  operated  by  an  electro-magnet  Tj,  local 
battery  and  key  Kj. 

Tlie  construction  and  operation  of  this  transmitter  is  fully 
described  on  pages  337  and  338. 

At  station  B,  the  receiving  instrument  R^,  having  a  polarized 
armature,  is  placed  in  the  circuit  of  the  line,  and  in  consequence 
of  the  polarity  of  its  armature,  will  respond  to  each  reversal  of 


Station  A. 


StaUon  B. 


Fig.  158. 

the  current  upon  the  line,  produced  by  tlie  movement  of  the 
double  current  transmitter  t^^  and  will  open  and  close  the  local 
circuit  of  the  sounder  Sj,  giving  signals  corresponding  to  the 
movements  of  the  key  Kj  at  station  A. 

The  line  at  station  B,  after  passing  through  the  receiving 
instrument  Rj,  is  conducted  to  the  earth  at  Gj. 

A  rheostat  X  is  inserted  l)etweoii  the  receiving  instrument  Rj 
and  the  earth,  the  resistance  of  wliich  may  be,  say,  from  two  to 
four  times  as  great  as  that  of  the  line.     A  key  Kg  is  connected 
with  the  line  in  such  a  manner  as  to  shunt  the  rheostat  X  by  a 
circuit  of  practically  no  resistance  each  time  the  key  is  depressed. 


848 


QUADRUPLKX  TELEGRAPHY. 


COMBINED   DII'LEX   AND   CONTRAPLEX   SYSTEMS. 


849 


In  order  that  the  operator  may  be  able  to  hear  his  own  sig- 
nals, the  key  Kg  is  provided  with  a  spring  contact  arm  k,  wliich, 
wlien  tlie  key  is  depressed,  is  l)rt)Ught  in  contact  witli  tlie  stoj)  J, 
tlius  shunting  the  rlieostat  X,  and  giving  the  signal  at  station  A. 
The  ordinary  contact  point  of  the  key  at,  or  nearly  at,  the  same 
time,  strikes  uj)()n  its  anvil,  and  closes  the  circuit  of  the  local 
battery  e  tlirough  the  sounder  <,  and  thus  duplicates  the  signal 
sent  to  the  other  station. 

At  station  A  a  receiving  instrument,  Eg,  having  a  neutral 
armature  and  adjustable  spring  r,  is  placed  in  one  of  the  wires 
leading  from  battery  K  to  the  double  current  transmitter.  The 
armature  of  the  receiving  instrument  Kg  opens  and  closes  the 
local  circuit  of  the  sounder  Sj,  in  the  ordinary  manner.  The 
retractile  spring  r  of  the  receiving  instrument  E^,  shotdd  be 
strained  uj)  to  a  sufficient  tension  to  withstand  the  attraction  of 
the  electro-magnet  when  the  rheostat  X  is  in  circuit  at  the  other 
statidii.  while  it  will  be  easily  overcome  by  the  increased  force  of 
t"ne  line  current,  which  results  from  the  shunting  of  the  rheostat 
X,  and  the  consequent  removal  of  its  resistance  from  the  circuit 
wiicnever  the  key  Kj  is  depressed. 

By  placing  the  receiving  instrument  Eg  in  one  of  tlie  wires 
leading  from  the  battery  to  the  pole  changing  transmitter  ^j,  the 
direction  or  ])olarity  of  the  curnmt  traversing  its  coils  is  never 
clianged,  and  consequently  its  armatun^  has  no  tendency  to  fall 
off  when  the  current  is  reversed  upon  the  line. 

It  is  obvious  tiiat  any  required  number  of  receiving  instru- 
ments similar  to  E,,  accompanied  with  the  other  ai)paratus 
shown  and  described  at  station  B,  may  be  placed  in  the  circuit 
of  the  line  at  way  or  intermediate  stations,  all  of  which  will 
simultaneously  respond  to  the  signals  given  by  the  key  Ki  and 
transmitter  <,. 

Fig.  159  is  a  modification  and  e^ctension  of  the  system,  so 
arranged  as  to  be  capable  of  either  transmitting  two  com- 
munications simultaneously  in  the  same  direction,  or  one  in  each 
diiection,  at  pleasure. 

If  the  keys  K^  and  K^  are  operated  at  the  same  time,  the 


350 


QUADRUl'I.KX   TKLEliUAI'HV. 


former  will  control  the  polarity  and  the  latter,  the  strength  of  the 
current  going  to  line  from  the  battery  E. 

At  the  terminal  station  B,  as  well  as  at  the  intermodiutc 
station  C,  receiving  instruments  E^  and  Jij  are  made  use  of,  tlie 
construetion  and  operation  of  whicli  are  fully  de^!cribed  on  pages 
338  and  340. 

The  polarized  armature  a  plays  between  two  contact  levers  N 
and  Np  whieh  are  held  against  the  stops  q  and  q^  by  springs  r 
and  rj  ;  tin'  springs  being  strained  up  to  a  tension  sufiicient  to 
resist  the  clrctroniagnetic  aetioii  of  tlie  weak  current,  which 
traverses  the  line  when  the  i-heostat  X4  is  ])ut  in  circuit  by  the 
ojiening  of  key  K4,  but  which  will  readily  be  overcome  by  tho 
stronger  current  which  passes  when  the  rheostat  is  cut  out,  by 
the  depression  of  key  K4. 

The  local  relays  M  M,  between  the  receiving  instruments  R^ 
and  Rj,  and  their  respective  sounders  S^  and  Sj,  at  stations  B 
and  C,  when  arranged  in  this  manner,  is  a  well  known  device  for 
reversing  tho  signals  of  the  relayS)  in  order  that  they  may  appear 
correctly  upon  the  sounder. 

Thus  it  will  be  understood  that  the  sounding  or  recording 
instruments  S4  and  Sg  at  stations  B  and  C,  will  respond  each 
time  the  key  K4,  at  station  A,  is  depressed,  while  in  like  maimer 
the  sounders  Sj  and  S3,  at  stations  B  and  C,  will  res[)ond  each 
time  the  key  Kj,  and  transmitter  t^,  at  station  A,  is  operatc-d. 

The  rheostats  X,  X3,  and  X4,  are  cut  out  of  the  circuit  when 
the  operators  at  the  respective  stations  are  not  using  the  line  by 
means  of  the  switches  AV,-  ^^3  ''"*^^  ^4*  precisely  as  in  the 
case  of  the  ordinary  closed  Aforse  circuit. 

In  order  to  transmit  communications  in  opposite  directions  at 
the  same  time,  the  operator  at  station  A  will  use  key  Kj,  and 
the  operator  at  station  B  or  C  will  use  key  Kg  f>i'K3- 

With  the  apparatus  constructed  and  arranged  as  in  fig.  159,  the 
operation  may  be  briefly  smnmed  up  as  follows : 

When  key  Kj  is  operated  sounders  Sj  and  S,  will  respond. 

When  either  K^,  K.,,  or  K4  is  operated  by  first  opening  the 
switches  attached,  sounders  Sj,  S4  and  S5  will  respond. 


COMIUNED   DIPLEX   AND   ■ 'ONTBAPLEX   SYSTEMS. 


351 


It  will,  tlioi'cforc,  b(!  readily  uuderstooil  that  tlic  following 
results  may  be  obtained  : 

1.  Station  A  may  send  a  mcssagi;  to  C,  and  C  at  the  same 
time  semi  one  to  A.  both  of  wiiich  may  Ih!  read  at  B. 

2.  A  may  send  a  message  to  B,  and  B  at  the  same  tiim;  send 
one  to  A,  both  of  whieh  may  be  read  at  C. 

3.  A  may  send  a  message  to  C,  and  at  the  same  time  B  may 
send  one  to  A,  which  latter  may  also  be  read  at  C. 

4.  A  may  send  a  message  to  B,  and  at  tlie  same  time  C  may 
send  one  to  A,  whieh  latter  may  also  be  r<'ad  at  B. 

5.  A  and  G  may  simultaneously  send  messages  to  B,  the 
latter  of  whieh  may  Ije  read  at  A. 

6.  A  and  B  may  sinmltaneously  send  messages  to  C,  the 
latter  of  whieh  may  be  read  at  A. 

7.  A  may  send  messages  to  B  and  (J  at  the  same  time. 

H.  A  may  send  two  messages  simultaneously  to  B,  both  <>f 
•which  may  be  read  at  C. 

9.  A  may  .send  two  messages  simultancou.sly  to  C,  both  of 
"whieh  may  be  read  at  B. 

10.  B  and  C  can  work  together  singly,  ])reeisely  as  in  the 
ordinary  closed  circuit,  Morse  system  :   and, 

11.  When  it  is  n(H  required  to  work  duplex,  A  can  signal 
B  or  C  with  either  of  his  two  keys. 

All  the  residts  which  have  been  described  are  accomplished 
by  means  of  a  single  main  battery  K,  i)laced  at  one  terminal 
Btiition  A. 

Fig.  160  represetits  a  comljination  of  the  above  system  with 
the  quadruplex  at  a  common  terminal  station,  at  whieh  the 
connections  are  so  arranged  as  to  allow  of  the  repetition  of  signals 
from  one  circuit  into  the  other. 

Taking  an  actual  case,  as  before,  we  will  suppose  the  repeating 
apparatus  to  be  located  at  New  London,  whieh,  for  convenience, 
maybe  designated  as  station  A.  This  is  in  eommunieation  with 
New  York,  12(5  miles  distant,  by  i\  ipia<lr\iplex;  wire  L,  and  with 
Norwich,  Conn.,  and  Woreestii-,  Mass..  by  the  line;  Lj,  73  miles 
in  length,  the  former  being  au  intermediate  and  the  latter  a 


852 


yUADRUPLEX   TELEGRAPHY. 


terminal  office,  whicli  wo  will  designate  respectively  as  stations 
B  and  C. 

The  ajiparatua  at  station  A  consists  of  a  complete  set  of 
qua(lni])lox  instruiaents  and  a  set  of  the  instruments  shown  in 
lig.  158,  both  of  which  have  already  been  dcscribod;  conse- 
(picntl}-,  it  will  only  bo  necessary  now  to  show  the  manner  in 
which  they  aro  worked  conjointly. 


Piij.  160. 

The  switch  or  button  w^  is  so  placed  between  the  local  bat- 
teries Bi  and  Cj,  that  when  closed  it  forms  a  part  of  each  of  the 
two  local  circuits  containing  the  sounder  Sj  and  transmitter  ij, 
hut  when  open  the  separate  circuits  are  combined  into  one  ;  and 
if  the  key  Ic^  be  closed,  the  relay  Ri  then  operates  both  sounder 


COMBINATION    (i|'   ylADKUIM.EX   A.VI)    DIIM.KX    SYSTEMS.     353 


2; 


S,  and  transmitter  /j,  and  tlms  repeats  the  signals  coming  from 
liiK^  L  into  line  Lj,  and  to  stations  IJ  or  (J. 

'I'lic  local  circuit  conttiiniiig  the  sounder  .1^  is,  in  a  similar 
manner,  separated  from  or  condnued  with  tiiat  containing  the 
transmitter  Tj  i)y  means  of  the  button  W,.  In  the  hitter  ease, 
relay  ?'i  operates  transmitter  '1\  as  well  as  sounder  .9,,  and 
thereby  repeats  the  signals  frum  L,  over  line  L  to  New  York. 

The  sounder  Sj,,  which  is  operated  by  tlic  relay  R„  of  line  L, 
may  be  arranged  in  connection  with  wires  1  iind  2  and  button 
jtfg,  so  that  when  the  latter  is  closed  and  key  /.'g  opened  the 
sluint  around  the  rheostat  X  is  thereby  extended  through  lever 
a  and  contact  0  of  sounder  S„  ;  and  thus  a  second  set  of  signals, 
received  from  New  York  on  relay  H3  at  station  A,  may  also  be 
repeated  into  line  L  and  to  stations  B  and  C. 

The  signals  produced  by  the  transmitter  Tg,  when  key  Kg  is 
0])cratcd,  are  received  at  New  York  upon  a  sounder  correspond- 
ing to  that  of  S3  in  the  figure. 

It  will,  therefore,  be  seen  that  witli  the  apparatus  thus  arranged 
the  following  results  may  be  olitaincd: 

1.  New  York  may  send  a  message  to  station  C,  and  at  the 
same  time  C  can  send  one  to  New  York,  and  both  be  read  at  A 
and  B. 

2.  New  York  may  send  to  B,  li  to  New  York,  and  both  be 
read  at  A  and  C. 

3.  New  York  may  send  to  C,  and  be  read  at  A  and  B, 
while  at  the  same  time  B  may  send  to  New  York,  and  be  read 
at  A  and  C. 

4.  New  York  may  send  to  B,  and  be  read  at  A  and  C^ 
whih'  C  may  send  to  New  York,  and  be  read  at  A  and  B. 

5.  New  York  may  send  to  B,  and  be  read  at  A  and  C, 
wdiile  C  also  may  send  to  B,  and  be  read  at  A  and  at  New  York. 

G.  New  York  may  send  to  C,  and  be  read  at  A  and  B, 
while  at  the  same  time  B  may  also  send  to  C,  and  be  read  at  A 
and  New  York. 

7.  New  York  may  send  to  B,  and  be  read  at  A  and  C,  and 
at  the  same  time  A  may  also  send  to  L,  and  be  read  at  C  and 
New  York. 


354 


QlADHri'l.EX   TEI.KGK.VIMIV. 


8.  New  York  may  'end  to  C,  iiml  be  I'ead  at,  A  and  B.  and 
at  the  sani(,'  time  A  may  also  send  to  C,  and  he  ivad  at  ]}  and 
New  Voi-k. 

9.  X(nv  York  and  station  A  may  work  dii])li>,\  conlinn- 
onsly,  witliout  I'ejrard  to  what  is  passniir  between  stations  A,  B 
and  "(A 

10.  New  York  may   send  two  nicssuii-es   simnUaneonsly  to 

A,  one  of  wiiidi  may  1"!  read  at  H  and  C,  and  at  the  same  time 
two  eonununieations  may  pass  over  tlie  line  to  New  York,  one 
from  A  and  the  other  from  C,  the  latter  of  which  may  be  read 
at  A  and  B. 

11.  N(nv  York  may  .send  two  mesi^ages  simultaneou.=jly  to  A, 
one  of  whieli  may  be  read  at  B  and  C,  and  at  the  same  time  rwo 
may  pa.ss  simultaneously  over  line  L  to  New  York,  oiie  from  A 
and  the  other  from  B,  the  latter  of  which  ma}''  be  read  at  A 
and  C. 

12.  New  York  may  send  two  ine.s.sages  simultaneously  to  B, 
both  of  ^vhieli  may  be  read  at  A  and  C,  and  at  the  same  time 
reeeive  two  from  A. 

13.  New  York  may  send  two  messages  simultaneously  to  C, 
both  of  which  may  be  read  at  A  and  B,  and  at  the  same  time 
receive  two  from  A. 

14.  New  York  may  send  two  messag>  s  .simultaneously,  one  to 
A  and  the  other  to  C,  the  latter  of  whicli  may  be  read  at  A  and 
B;  and,  at  the  same  time,  n^eeive  two.  one  from  A  and  one 
from  C,  the  latter  of  which  ma}'  be  read  at  A  and  B. 

15.  New  Yolk  may  send  two  messages  simultaneously,  one 
to  A,  the  other  to  B,  and  the  latter  be  read  at  A  and  C ;  and, 
at  the  same  lime,  reeeive  two,  n\w  from  A  and  the  other  fi-om 

B,  the  latter  of  which  may  be  read  M  A  ami  C. 

16.  N(>w  Yoi'k  may  receive  two  n.es.sages  simultaneously 
from  A,  and,  at  the  same  time,  transmit  two  di.stinet  communi- 
oations.  one  to  B  and  one  to  C.  or  both  to  eit 


arately,  and  both  may  be  read  at  A.     Finally, 

17.    Station   A  may,  by  projierly  arranging  the 
Wo  and  AW.  divide  the  two  lines  L  and  L,,  and 


station 

buttons 
^l)erate 


P- 


each 


anil 
Ihi 


cin 


yrADllfPLEX    UEl'K.VTKK. 


355 


sciiaratcly  :  llie  foninT  as  a  quailnijiU'x  wire  to  Ntnv  York,  tlie 
liiUcr  as  cuiitiaple.    ■  ■'  diplex  to  15  and  C. 

V\ji.  161  shows  a  ],laii  oi  roniu'ctiiifi;  tlie  apparatus  at  a  station 
fonniii,!^  llic  coimnoii  teiMiiiiius  ol'  two  (piadniplrx  ciiviiits,  s<j 
as  to  repeat  from  one  into  the  otiier.  We  will  sujjjjose  the 
station  to  lie  Cle\elan(i.  and  tliat  Lj  represents  a  ([uadniplex 
■wire  extending  from  thai  jioint  to  Ikul'aln,  a  distance  of  183 
milt  ■■.  and  Lg  a  similar  wire  between  Cleveland  and  Cineinnati, 
a  distance  of  250  miles.  The  apparatus  oom]irises,  in  addition 
to  two  complete  sets  of  quadrni)lex  instruments,  the  foiir  Initton 
switelies,  W,  Wj,  Wg  arid  W3,  wliieh  serve  for  giviiifx  direct 
through  communication  lietween  Buffalo  and  Cincinnati,  or  for 
dividing  the  wires  and  tlius  allowing  eacli  of  them  to  lie  worked 
separately. 

For  olearnessof  illustration,  the  relays,  as  shown  in  the  figure, 
ai'c  not  wound  dillcrenlly,  and  the  rheostats  and  condensers  form- 
ing the  artificial  liiu^s  ha\e  been  omitti^d. 

The  arrangement  of  tiio  local  circuits  of  the  several  relays 
Jlj,  Itg,  r^  an<l  j'j,  so  that  they  may  be  separated  from  or  com- 
bined with  those  of  transmitters  /j,  /j)  '^\  !"i'l  'i\  respectively, 
by  means  of  the  buttons  W.  W,,  W,  and  AV.,,  is  i)rccisely  the 
same  as  that  shewn  in  lig.  157,  iov  re[)eating  from  one  quadru- 
plex  into  two  duplex  circuits,  and  vice  versa. 

It  will  therefore  be  understood,  from  what  has  already  been 
said,  that  when  the  buttons  are  all  ojhmi,  and  the  keys  Kj,  K^, 
/.•j  and  /Cjj  closed,  IJutTalo  may  transmit  two  eomnuinications 
simultaneously  over  the  line  L,  to  Cleveland,  where  they  will 
then  be  automatically  retransmitted,  one  by  relay  r,  ;ind  trans- 
mitter Tp  the  other  by  re'ay  r„  and  transmitter  T^.  over  line  Lg 
I0  Cincinnati.  The  latter  station  may  also  transmit  two  inde- 
pendent messages  at  the  same  time  to  Cleveland,  where,  in  l>irn. 
I  hey  will  be  retransmitted,  one  by  relay  R,  and  transmitter/,, 
and  the  other  by  relay  lU  and  transmitter  1.,,  over  line  L,  to 
Jbill'alo. 

By  simply  (dosing  the  buttons  W,  W,,  \V„  and  W^,  the  two 
circuits  liiay  be  divided   at  Cleveland,  and   worked  .sejiarately. 


356 


QUADliUPLKX  TELEGHAI'IIY. 


Ml 
(1? 

^v 
III 


QUADKri'LEX    KEPEATER 


357 


A 


/ 


_^ 


III  regular  practice,  liowevcr,  the  circuits  are  worlced  in  tlio  fol- 
lowing manner,  so  as  to  facilitate  the  exchange  of  husinesa 
between  tlie  three  points  l>eforc  mentioned  : 

The  buttons  Wg  ami  Wg  arc  closed  and  W  and  Wj  opened. 
When  thus  arranged,  llnlTalo  and  Cincinnati  are  enabled  to  work 
together  duplex,  and,  at  the  same  time,  Cleveland  may  work 
duplex  to  Buffalo  over  lino  Lj,  and  to  Cincinnati  over  line  Lg. 
The  transmitter  /j  and  relay  r^  of  line  Lj  arc  so  located  on  the 
desk  or  table,  with  regard  to  the  corresponding  a])paratus  (^f  line 
Lo,  as  to  facilitate;  the  adjustment  of  the  several  instruments. 

Quadruplex  r(>peaters  are  similarly  arranged  for  facilitating 
the  exchange  of  business  betvi'een  numerous  other  })oints  on  the 
lines  of  the  Western  Union  Telegraph  Company,  among  which 
maybe  mentioned  Boston,  Albany  and  Buffalo;  Bull'alo,  De- 
troit and  Chicago  ;  and  New  York,  Hartford  and  Providence. 

A  combination  of  the  two  methods  of  du])lex  telegraphy, 
known  as  the  bridge  and  differential  systems,  but  differing 
materially  in  arrangement  from  that  sliDwn  on  page  311,  is  also 
used  in  practice.  At  Buffalo  two  comj)lete  sets  of  (piadniplcx 
ajiparatus,  on  this  plan,  arc  arranged  by  connecting  the  local 
circuits  in  prcei.scl'*  'he  same  manner  as  shown  in  lig.  161,  for 
repi'ating  signnls  irom  one  circuit  into  anotiicr,  and,  by  this 
means.  New  York  and  Chicago  are  enabled  to  exchange  four 
ccmmunieatious  simultaneously,  over  a  single  wire,  between 
these  ])oints, 

A  second  wire  b<>twe(Mi  New  ^'ork  and  Cliicago  is  equipped 
with  the  quadruj)lex  aj)paratus,  and  ])reeiscly  the  same  arrange- 
ment as  the  al)ii\e  is  made  at  Buffalo  fnr  repeating  from  one 
circuit  to  the  other.  At  N(nv  ^'n^k,  howevi^-,  the  connections 
arc  such,  lli;ii  while  itsnllice  and  ('liicagi>  ;n'c  working  ilnplcx 
on  one  side,  the  latter  may  also  woi'k  duplex  on  tiie  otluM"  side 
with  liny  one  of  two  or  nioi-e  bnnich  ollices  in  New  Yoi'k.  The 
manner  in  wliich  this  is  done  will  readily  be  understood  from 
fig.  I(i2  and  the  following  ex|il;nKition,  v/hich  n'liilc  to  the 
arrangement  for  a  l^oston  wire,  where  it  was  llrst  used  ;  the  one 
for  the  Cliicago  line,  however,  is  just  the  same  : 


858 


yr.ADuri'LKX  THr.EciHAi'iiv, 


The  complete  quadniplex  set  in  ('(Hiiicctiou  witli  tlie  line  L  is 
supposed  to  1k'  at  the  New  York  main  ollice.  Soiuulers  .s,  and 
S^,  and  key  k^,  at  a  braneli  olliee  in  tin;  city,  which  we  will  cull 
station  A  ;  and  the  a]iparatii.s  consistinj^  of  sounders  .vj  and  S3, 
rep(>ating  relay  Wj)  '"•'^'.V  ^'^"2  '""^  Icx-al  ])atteiy  e^,  at  a  second 
branch  ollice,  ■which  \vc  will  call  B, 

In  order  to  provide  for  the  simultaneous  rece[)tion  of  two 
independent  conununications  over  line  L,  from  Boston,  one  of 
which  shall  be  received  upon  rchiy  11^  and  sounder  Sj,  and,  at 
tlie  same  time,  also,  ii[)on  sounder  s^  at  station  A,  and  that  the 
other  shall  be  received  upon  relay  Rj,  souiuler  Sj  and  u[ion 
sounder  Sg  at  station  B  as  well,  while  se[)arate  communications 
are  at  the  same  tiuK^  bein<f  sent  to  Boston  from  each  of  the  two 
stations  A  and  15,  it  is  only  necessary  to  connect  the  hjcal  or 
V)ranch  lines  with  tlio  relays  and  transmitters  of  the  quadraplcx 
a[>paratus  at  the  main  olUco  in  the;  manner  shown  in  the  diagram 
(lig.  162j.  Here  the  route  of  th(!  local  or  branch  wire  of  the 
relay  Rj  maybe  traced  from  the  earth  plate  G^  at  the  main 
office,  to  battery  e,  wire  1  and  armature  of  relay  Rj  to  sounder 
Sj,  and  thence  by  wire  Ij  to  sounder  Sj  and  earth  (i„  at  station 
A.  The  route  of  the  branch  circuit  of  relay  II3  is  from  earth 
plate  CT3  to  battery  c^.  wire  2,  armature  of  repeating  sounder  M 
and  sounder  Sj,  and  thence  by  line  I3  to  sounder  Sg  and  earth 
G4  at  station  B.  The  routes  of  transmitters  T^  and  Tg  may 
be  similarly  traced,  It  will  be  noticed,  however,  that  the 
arrangement  of  the  branch  line,  as  well  as  local  conned' ins  of 
transmitter  Tg,  differ  materially  from  those  of  Tj,  as  in  it  nor- 
mal position  the  former  should  remain  opei.,  and  thus  leave 
only  the  smaller  portion  of  tliL' main  battery  on  'le  line.  The 
keys  Kj  and  k^  are  not  provided  with  circuit  iwsi.ig  switches, 
and  contact  is  nuuh;  at  the  back  point,  instead  f  the  front,  as  in 
the  ordinary  form.  The  normal  position  of  these  keys  is  that 
.shown  in  the  ligure.  in  which  they  close  the  branch  ci.cuit  and 
cause  the  arin.ature.s  a  and  «,  of  repeating  relays  m^  and  ?»._,  to 
be  attra<!ted,  and  thus  brejdc  tl^!  local  circuits  of  transmitter  T, 
at  the  main  ollice,  and  sounder  S3  at  B,     By  dci)ressing  Kg  or 


Ut;. 


AKRAXCEMEN.    Foil    liliANCU    OFFK'ES. 


359 


A-g,  and  consequently  brCcaking  the  hrandi  circuit,  the  armatures 
of  tlic  repeating  relays  vi^  and  iii,^  v,  ill  he  released,  and  the 
local  circuits  of  transmitter  Tj  and  sounder  S,  will  bo  closed 
simultaneously.  The  operator  at  B  is  thus  enabled  to  hear  his 
own  or  other  signals  that  arc  being  transmitted  by  the  main  or 
other  ofTicc  on  the  l)ranch  line. 

r ■'- OO 


It   ■will   therefore   be   sufficiently   ol 


.1  fr 


tl 


reeeiveil  Irnni  the  line  h  upon  relay 


J{, 


)V1(>I1> 

am 


that    th 


i--nal 


main  o 
station 
g  tl 


iUeo 


can,  w 


ith  equal  faeility,  bo  read  from  s< 


milder  ^,  at 
)Uiii!i'r  s 


will 


le  the  latter  ofheo  at  the  same  time  i 


iiav 


ly  iie[ 


I 
)riv 


ni 


10 


cev 


am 


I  euiisei(neiitly  operating  sounder   S.,   a 


traiisniitler 


nil 


iM'iineh 


1)0  sen(bng  signals  to  Boston  or  to  some 
)ffiee  at  that  place.     In  a  similar  manner  and  at  the  same  time, 


360 


QLADKUPLKX   TKLKCiKAl'liY. 


station  B  may  workdvijilex  witli  aiiotliorlirancli  office  at  Boston, 
of  wliieh  at  that  j)laco  tlieru  an'  Jive  on  one  sido  of  the  (juadru- 
plex  and  two  on  the  otlier.  Tiie.  balancing  and  adjusting  of  the 
quadrnplcx,  it  will,  of  course,  bo  understood,  is  all  done  at  tlio 
main  office. 


A^i  .- 


Fij.  ic: 


The  qnadruj)lcx;  is  also  arranged  to  work  in  connertion  with 
.1  single  direct  circuit  containing  any  nuinbci'  of  ulliccs,  and  the 
plan  has  been  found  to  serve  an  ivxccllcnt  ])urpose  in  pi'actici^,  as 
coniniunit'uti'in    can  thrrebv  br  ui.iintaim'd    between  a  distant 


gUAURUl'LEX   AND   SINCILK   CIKCUIT   COMBIVATION.        ',',01 

ollit'(^  (HI  the  (i[u;ulruj)lex  circuit  ami  any  one  of  tlu^  ninnlxT  on 
the  single  wire  line. 

Fig.  163  shows  the  details  of  the  arrangement  as  a(loj)tc<l  at 
St^  Louis,  for  automatically  repeating  from  one  circuit  into  the 
other,  the  outfit  consisting  of  one  conqjlete  set  of  (piadruple.x. 
apparatus  and  2)ortions  of  a  Milliken  rejicater.  The  line  L,  ex- 
tending to  Chicago,  280  miles  distant,  is  connected  with  the 
quadrn])lcx  relays;  and  line  Lj,  extending  to  Kansas  City, 
Atchison,  Leavenworth  and  St.  Joseph,  with  the  ^[illikeu  re- 
lay rj.  Tiie  local  circuit  of  this  relay  is  separated  from  or  con- 
nected with  that  of  the  tran.smitter  Tj  by  means  of  the  switch 
Wj,  in  ])reci.sely  the  same  manner  as  in  the  preceding  cases, 
and  by  means  of  the  switch  Wg,  the  local  circuit  of  relay  R^ 
may  be  extended  through  the  transmitter  ij,  or  disconnected 
therefrom  at  jileasnre.  With  the  switch  Wg  tu)-ncd  to  the  right, 
for  example,  as  bhown  in  the  figure,  the  local  circuit  may  be 
ti'aced  from  the  switch  to  local  battery  Eg,  wii'(!  1,  transmitter  tj^ 
and  wire  2  to  relay  R^,  thence  by  wire  8,  sounder  Sj  and  bat- 
ti'ry  E[  back  to  the  switch  again.  When  it  is  turned  to  the  left, 
battciy  Kj  and  transmittiM- 1^  are  thrown  out  of  circuit  and  relay 
Rj  operates  sounder  S^  alone.  The  local  contact  jwints  at  the 
front  end  of  transmitter  t^  are  shunted  out  when  desired,  by 
means  of  the  button  or  switch  w^  ;  and  the  main  contact  points 
at  the  opp{)site  end  of  th(>  lever  ar(^  in  like  manner  cut  out  by 
means  of  button  W.  When,  therefore,  the  switches  W,.  lo^ 
;;nd  W  are  open,  Wj  turned  to  the  right  and  keys  Kj  and  k^ 
elo.sed,  as  shown  in  the  figure,  Chicago  may  exchange  business 
with  any  one  of  theoflices  on  Lj,  the  signals  being  automatically 
r(^trans?nitted  at  St.  Louis  by  relays  llj,  r^  ami  transmitter  T, 
and  <,.  At  the  same  time  St  Louis  ami  Chicago  may  also  work 
du]ilex,  using  key  Kg  and  Rg  for  that  purpose. 

By  closing  switclns  W,,  lo^  and  W  and  turning  Wg  to  th(> 
left,  the  two  lines  Ij  and  L,,  as  will  readily  be  scvmi,  may  be 
worked  separatiMy,  tin;  former  as  a  i[uailruplev  and  tlii^  latter  as 
a  single  Morse  circuit 


362     AHUANQEMENT   FOR   NEL'TUAM/IN<J    CUUUENT   I.VJ)rCTlUN. 


C'fHRENT    INDrcTloN'. 

The  intcrfoTonoo  l)Otw('cn  well  insulated  telofrrapli  lines,  known 
as  current  induction,  has  from  tlic  lirst  done  a  great  deal  toward 
[ireveuting  tlie  i)r()[)er  working  of  the  ((uadruplex  system,  and 
the  question  as  to  how  the  disturbing  elTeets  due  to  this  cause 
might  be  overcome  has,  therefore,  become  one  of  considerable 
importance. 

Mr.  Charles  ][.  Wilson,  of  Chicuigo,  who  has  given  consider- 
able attention  to  the  subject,  has  devised  a  plan  lor  diminishing 
the  difliculties  just  referivd  to. 

Mr.  Wilson  seeks  to  a(!complish  his  object  by  establishing  a 
counter  current  iu  tlic  disturbed  conductor  at  the  same  moment 
and  of  the  same  strength  and  duration  as  that  of  the  induced  ctu"- 


Fi>j.  \Gi. 

rent  which  is  generated  iu  it  by  the  sudden  change  of  potential 
in  a  neighboring  wire. 

Fig.  164  shows  the  api)lication  of  the  method  to  a  single  Morse 
line,  but  here  it  is  of  com])aratively  liUle  practical  importance, 
fi'om  the  fact  that  these  lines,  as  a  general  thing,  can  be  su[)plie(l 
with  strong  currents,  so  that  there  is  always  sufRcient  working 
margin  to  cover  the  difficulties  arising  from  induction.  The 
primary  wire  of  the  induction  coil  C  is  in  the  circuit  of  one 
line,  and  the  secondary  coil  in  that  of  the  other.  The  coils  arc 
so  wound  or  connected  to  tin;  lines  that  either  will  induce  in 
the  other  currents  of  opjiosite  direction  to  llio.se  induced  by  the 
remaining  jKirts  of  the  circuit.  TIk;  electro-magnets  represented 
at  a,  a',  h  and  A  ,  are  employed  for  ])rr)(liicing  the  |)ro[)er  retard- 


nvx  e 


fTcct 


on    the  counter  or   neutrah/ing  currents  which   are 


generated  in.  the  coi's  surrounding  (J,  and  the  adjustable  resist- 


JNDIC'IKi.V    JIKTWKKN'    I'AKA  l,l,l-;h    I.IN'ES. 


363 


anoe  li  R  (ifllu!  shunt  circnit  scr\n  to  still  furtlier  modifv  these 
(•iinvnts,  so  that  their  iietion  is  sulijcct  to  coiuplcte  couti-ol. 

Tlu;  luaiiner  in  which  the  cleviro  is  rcmlerLMl  ell'ective  will 
roiidily  1)o  understooil  from  tlic;  diiigram.  Tiius,  for  iiist,'in(:'(\  if  a 
current  of  any  polarity  is  sent  into  thceondnctor  A,  a  current  of 


LmB 


Fi'j.  k;,".. 

tlie  opposite  polarity  will  In;  induced  in  tlie  line  B,  owing  to  its 
elose  ])roxiniity  to  the  f<irnier,  l)ut  at  the  same  instant  a  similar 
current  will  also  be  induced  in  the  coil  to  which  it  is  joined,  and, 
as  the  couuection  is  so  arranged  that  this  current  oi>poseri  that 


ijm 


Fi'j.  I  GO. 

inducc(l  b\'  the  ])roximity  of  the  two  conductors  tc)  one  another, 
the  proper  action  of  tlu;  instruments  will  not  Ih^  disturbed. 

Tlie  arrangcmeni  for  accomplishing  the  sauK;  result  between 
two  ([uadruplex.  circuits  is  shown  in  lig.  [(io.  It  is  evident  that, 
with  the  bridge  or  dilferential  principle,  all  that  is  re(pui'ed  to 
ellect  the  end  in  \iew,  is  to  cause  the  two  artilicial  lines  to  act 


864 


DOUBLE   TRANSiMISSIOX   IN'   THE   SAME    WUECTION. 


upon  Oiicli  otlii'i'  ill  a  luiiniu'r  similar  to  tlio  uclioii  of  tlic  actual 
lines,  and  for  this  jmrposo  an  induction  coil  and  system  of  mag- 
nets, similar  to  that  just  described,  k  inserted  in  the  jiath  of  the 
two  artificial  lines  at  I. 

Fig.  166  shows  an  arrangement  of  condensers  substituted  for 
the  induction  coils,  which  has  been  in  extensive  use  on  some  of 
the  long  lines  in  the  (;eutral  division  of  the  Western  Union 
Telegraph  Company.  If  the  inductivo  effect  of  the  two  wires 
are  eriual,  the  condenser  E  is  alone  necessary  to  effect  the  neu- 
tralization ;  but  when  unerpnd,  the  two  condensers  ^  and  G 
are  required  in  connection  with  1*]. 


EAKLV    MKTIIODS     OF    SIMI'LTA.NKOUS    TUANS.MISSIOX    IN    THE 
SAME    DIUECTION. 

In  October,  1855,  A.  Bernstein,  of  Uerlin,  devised  a  plan  for 
the  simultaneous  transmission  of  two  messages  in  the  same 
direction,  which  is  shown  in  fig.  107. 

The  transmitting  ai)[>aratus  consists  of  two  independent  cir- 
cuit preserving  keys  Ivj.  and  Kg  in  connection  with  batteries 
Bj  and  Bj,  the  former  composed  of,  say  10,  and  the  hitter  20 
cells,  as  shown  in  the  ligiire  at  station  A. 

The  movements  of  these  keys  produce  three  different  electrical 
conditions  in  the  line,  according  to  their  respective  i)ositious  with 
reference  to  each  other,  as  follows: 

1.  First  and  second  keys  open.  The  route  of  the  circuit  may 
be  traced  as  follows:  From  the  earth  ]>late  (x,  through  wire  6, 
adjustable  stops  5  and  4,  wire  3,  to  adjustable  stops  1  and  2  and 
line  L.  This  m;iy  be  considered  the  normal  condition  of  the 
keys,  in  which  jiosition  no  current  passes  to  the  line. 

2.  First  key  <;losed  ami  second  key  open.  The  route  is  from 
earth  plate  0  to  wires  6,  7,  niain  baltery  B,,  thence  to  lever  l^ 
of  key  K  p  and  wire  8  to  stops  2  and  1  an<l  line  L  to  distant 
station  as  Ijcforc  In  this  jiosition  of  the  keys  the  smaller 
battery  J^^  only  is  in  circuit,  sending  to  the  line;  a  positixT  or  -]- 
current  of  -|-  1(1. 

3.  Second  key  chased  and  lirst  key  open.      The  route  now  is 


B 
dil 

ofj 

col 


ail 


BEUNSTKIN  S    MKTIlUUS. 


305 


from  onrtli  plate  G,  wire  C),  to  stops  5  iiiid  i  ;  thcnco  Ly  wire.!  3 
and  cS,  to  main  tiattcrv  Bo.  iin<I  lever  L,  of  key  K^,  ;  thence  l>y 
wire  U  to  stop  1,  ami  lino  L  to  distant  ollice.  In  this  position  ol" 
the  keys  tiio  lari^-er  battery  Bj  only  is  in  t^ircuit,  sending  to  line 
a  positive  or  -f-  enrrent  of  -f-  20. 

•1.  First  and  second  keys  both  depressed.  The  route  of  the 
eirciiii  in  this  case  is  from  earth  plate  G,  wire  (!,  7,  to  battery 
Bj,  le\er   /j  ;   thenco  to  stop   4,  and    wires  8,  H,   and   Ijattcry 


for 


iVy.  167. 

Bj  to  lever  l^,  wire  9  to  stop  1  ;  thence  to  the  line  L  and 
distant  station  as  before.  In  this  position  of  the  keys  both 
batteries  are  in  circuit,  S'Midiu'jr  to  line  a  positive  or  4-  current 


of  +  30. 


At  station  B  a  rcceiviui.-  instrument  oi  relay  is  made  use  of, 
composed  of  a  single  elcctrt>-magnet  M,  having  thnje  armatures 
li,,  ll„  and  Bo,  to  each  of  wliich  an;  attached  retractile  springs 


'.3' 


;ti 


aid  ?•,  respectivclv,  Witli  local  cu'cuits  and  so 


und 


ers  S, 


anc 


IS 


2) 


as  sliown  m 


the  1 


igure. 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


// 


4. 


:/. 


% 


W/. 


1.0 


I.I 


m 


2.5 


2.0 


1.8 


L25  iU   ii.6 


%' 


7 


y 


-^ 


Photographic 

Sciences 

Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y.  14580 

(716)  872-4503 


306 


DOLliLE   TKAXSMISSIOX   IN'   TIIK   SAMK   DIKECTIOV. 


Sounder  >Sj  sliould  ]v.s|)on(l  solely  to  llic  movements  of  key 
Kj,  and  sounder  So,  in  like  manner,  to  tliu  movements  of  key 
Kj,  while  both  should  responi'  wlien  keys  K,  and  Kj  are 
simultaneously  dejjressed. 

Tlie  manner  in  wliieh  tliis  result  is  attained  will  be  under- 
stood by  referenee  to  the  following  explanation  of  tlie  efTeet  of 
each  of  the  previously  mentioned  electrical  conditions  of  the 
line  upon  the  receiving  instrument  M  at  station  B  : 

1.  The  normal  condition  of  the  transmitting  aj)paratus. 
No  current  to  line. 

The  local  circuit  of  sounder  Sj  is  open  at  ]ioint  o,  armature 
Kj  being  held  against  its  back  stop  by  the  retractile  force  of 
spring  r,. 

Armature  Itj  is,  in  a  like  manner,  held  against  its  back 
stoj), 

.'.nuature  R3  rests  ^ipon  its  back  stop,  owing  to  the  retractile 
force  of  spring  r^,  in  which  position  it  will  be  observed  that  a 
local  circuit  is  comj)leted,  in  which  are  included  sounder  S3  and 
both  local  batteries,  but  as  the  two  latter  have  like  poles  together, 
their  eflfect  ujwn  sounder  Sg  is  sul)stantially  neutralized;  con- 
serpiently,  the  latter  remains  inactive. 

2.  Positive  current  from  battery  B,  only  :=  -|-  10. 

The  local  circuit  of  soun<ler  Sj  is  closed  between  the  j)oint 
0  and  armature  11,,  because  the  action  of  the  current  upon  the 
relay  M  is  strong  enough  to  overcome  the-spring  r,,  and  force 
armature  R,  iigainst  the  stop  0. 

Armature  M^  remains  on  its  back  stop,  because  the  power 
of  the  current  u])on  the  line  is  not  sufficient  to  overcome  the 
tension  of  si)ring  r^. 

Armature  R3  rests  u]^on  its  back  stoji  because  the  cun'cnt  la 
m)t  strong  enough  to  overcome  the  spring  r^.  As  in  the  fii"st 
case,  it  will  also  be  observed  here  that  armature  R,,  in  this  posi- 
tion, completes  a  local  circuit  in  which  is  included  sounder  S3. 
The  latter^  however,  remains  inoperative,  for  the  reasons  before 
explained. 

3.  Positive  current  from  battery  Bj,  =  -f-  20. 


BERNSTEIN  S   METHODS. 


3t57 


Tho  local  circuit  of  sounder  .S„  is  closcil  between  tliC  contact 
])oint  tmd  aniiature  Ilj,  because  the  power  of  the  line  current  is 
sufficient  to  overcome  the  spring  r^,  and  move  the  armature  1l^ 
a^-Oiinst  its  contact  i)oint.  Armature  11^  still  remains  on  its  l)ack 
stop,  because  the  current  upon  the  line  is  not  of  sufficient  strength 
to  overcome  the  tension  of  s])ring  r^  In  order  to  prevent  a  false 
signal  from  being  given  by  sounder  S,,  it  is  obviously  essential, 
in  this  case,  that  armature  Ej  should  make  contact  with  the 
]>oint  0  simultaneously  with  armature  1^,,  bv  which  means  the 
local  bat1(!rv  of  sounder  Sj  is  short-circuited,  thus  leaving  the 
latter  moperative. 

4.  Positive  current  from  both  batteries  (B,  and  Bj)  =  -|-  30. 

The  current  upon  the  line  in  this  case  is  sufllciently  j)owcrrul 
to  overconu'  the  tension  of  the  retractile  springs  r,,  r^  and  r^, 
and  force  the  armatures  Rj,  Rj  and  R3  against  their  resj)eetive 
front  sto]is  o  and  0,,  operating  the  sounders  S,  and  Sj. 

Thus  will  be  understood  the  manner  in  wiiich  the  resju'ctive 
armatures  of  the  receiving  instrument  are  made  to  assume  their 
diflerent  jxisitions  with  relation  to  the  electrical  condition  of 
the  line,  so  as  to  record  the  j)roper  signal  upon  sounders  Sj 
and  Sg. 

Instead  of  the  receiving  instrument  as  devised  by  Mr.  Bern- 
stein, viz. :  a  single  electro-magnet,  with  three  separate  arma- 
tures, of  different  adjustments,  three  independent  relays  may  be 
used,  with  local  connections  the  same,  without  dej)arting  from 
the  principle  thereof. 

A  second  method  was  also  inviMited  by  Bernstein,  in  which 
he  made  use  of  both  i)ositive  anil  negative  cui'rents. 

liefcrring  tio  the  diagram,  iig.  108,  it  will  be  observed  that  the 
transmitters,  or  kcvs,  arc  circuit  i)reserviiiir,  the  sketch  ditleriuir 
from  the  original  iu  form,  but  not  in  ]>riiiciple. 

The  operation  of  the  two  keys  gives  rise  to  three  strengths  of 
eurrent  upon  the  line,  according  to  their  respective  positions, 
with  reference  to  eacli  otiier,  as  follows: 

The  normal  ]K)sition  of  the  keys  is  that  shown  m  tlie  figiuv, 
both,  being  o])cu. 


308        DOIHLK   TKAXSMlgSION    IN   THE   SAMK   DIUPXTION. 

Tli(>  ronU'  (if  tlio  eircMiit,  in  each  of  the  before  ineiitionod  posi- 
tioiis  of  the  keys  Ky  ami  K;,,  may  he  readily  traced  hy  reference 
to  the  drawing. 

Key  Kj  alone  sends  a  positive  or  -\-  current  of,  say,  10  cells 
from  battery  R. 

Key  Ko  alone  sends  a  negative  or  —  current  from  the  same 
battery  =,  —  10. 

When  both  keys  are  simultanooasly  depressed,  the  negative 


B 


9   T- 7 


1 


a 


Fig.  168. 


pole  of  the  smaller  battery  is  iasulatcd,  and  the  larger  battery 
lij  sends  a  i)o.sitivc,  or  -f-  current  =,  -j-  20. 

Bernstein's  receiving  apparatus,  in  this  case,  is  composed  of 
tiircc  independent  relay.s,  polarized  by  means  of  the  auxiliary 
local  coils  lip  Kg  and  11,,  the  two  former  being  constant,  and 
the  latter  controlled  by  the  armature  a^  of  relay  M2,  as  shown 
in  the  figure  at  stiition  B. 

The  sounders  S,  and  S3  are  operated  by  shunting,  instead  of 
opening  and  closing  the  circuit 


ill 

P 

sti 

So 


of 

th 


BKRXSTETNS   METHODS. 


369 


The  strengtli  of  the  current  in  each  of  the  anxiliary  IncrJ  cir- 
cuits l)ef()re  mentioned  may  Ik;  cliangecl  at  will,  ]>y  \iir\  in<;  the 
adjustable  resistance  coils  r^,  r^  and  ?•,.  It  should  not,  how- 
ever, Im!  of  sullieient  power  to  overcome  the  tension  of  »i)rings 


Sj,  ^2  and  Sg. 


Tiie  current  from  auxiharv  local  R,,  circulating  in  Mj,  13, 
say,  =  -(-  10,  and  that  of  auxiliary  local  E,,  circulating  in  ^^2, 
=  — 10.  'J'hat  of  relay  Mj  is  brought  into  action  only  when 
armature  a^,  of  relay  M2,  makes  contact  with  stop  0,  at  which, 
time  a  current  of  -j-  10  circnhites  through  M,. 

Bearing  this  in  mind,  it  will  be  readily  understood  by  the  fol- 
lowing e.xiilanation  how  the  armatures  Oj,  a^  and  O3  of  the 
receiving  in.struments  ]\r,,  W,,  and  M3,  respectively,  are  matle 
to  assume  positions,  with  relation  to  the  three  electrical  condi- 
tions of  the  line,  .so  as  to  cause'  sounder  S,  to  respond  solely  to 
the  movements  of  key  Ivj,  and  .soui;dcr  So,  in  like  maimer,  to 
the  movements  of  key  K^,  whiK'  both  rcs[)iind  when  Kj  and  Kg, 
at  the  .sending  stati(m,  arc  simultaneously  dcpre.-iscd. 

1.  Kj  alone  depres.sed,  a  positive  or -j- '-'ii'i'''iit  to  the  line  of 
-f- 10.  The  strength  of  this  current,  supplemented  by  that  of 
the  auxiliary  local  Kj,  is  sufi'iciciit  to  dvercomc  the  spring  s^, 
and  move  the  armature  o,  forward,  thus  breaking  the  shunt 
bet\»  >cn  stop  Pj  and  armature  ai,and  leaving  sounder  Sj  t(.)  be 
actuated  by  local  battery  /,. 

The  action  of  the  line  current  upon  relay  ^f.^,  in  this  case, 
tends  to  partially  neutralize'  the  ell'ect  of  the  auxiliarv  coil  Kg  ; 
con.secpiently,  the  armaturt;  «„  is  held  more  lirmly  by  spring  s^ 
in  the  jiosition  shown. 

Armature  aj,  of  relay  M3,  also  remains  on  its  back  stop 
P3,  1  ecause  the  line  current  (viz.  :  -\-  10:)  is  not  of  sullieient 
strength  to  overcome  the  s|>ring  s^.  Tlnis  the  shunt  around 
.sounder  Sj  remains  unbroken,  and  the  latter  is  inoiierative. 

2.  Key  K2,  depressed. 

A  negative  or  —  current  of  —  10.  In  this  case,  the  polarity 
of  the  line  current  is  such  as  to  partially  neutralize  the  etfcct  of 
the  auxiliary  local  Uj.    The  armature  a^  is,  in  consecpienec,  held 


370 


DOUBLE  TRANSMISSIUX   IX   THE   SAME   DIKECTIOX. 


more  securely  by  spring  Sj  against  stop  Pj,  thus  preventing  a 
signal  being  given  on  sounder  Sj. 

Armature  a^  of  relay  Mj  is  carried  from  stop  V^  *^°  ''i  because 
the  strength  of  the  line  cun-ent,  viz. :  —  10,  atUled  to  that  of  the 
auxiliary  local  ( —  10),  is  sufficient  to  overcome  the  tension  of 
retractile  spring  Sj,  thus  breaking  the  shunt,  and  causing  local 
battery  l^  to  operate  the  sounder  Sg. 

It  will  here  be  observed  that  when  armature  Og  connects  with 
sto|i  0,  the  auxiliary  local  of  relay  M3  is  closed,  the  strength  of 
wliich  (viz. :  -|-  10)  being  the  same  as  that  froiu  the  line,  but  of 
o])j)osite  polarity,  it  only  serves  to  substantially  neutralize  the 
effect  of  the  latter  upcjn  relay  ^fj,  and  armature  Oj  is  held 
inactive  by  the  retractile  spring  Sj. 

3.  Keys  K^  and  Kg,  botli  depressed. 

A  positive  or  -|-  current  of  -\-  20. 

Armature  a^  of  relay  M^  is' caused  to  move  forward,  thus 
breaking  the  sliunt,  and  allowing  a  current  from  local  battery  /, 
to  operate  sounder  Sj.  The  line  current  in  this  case  is  of  a 
polarity,  and  sufficiently  powerful  to  completely  neutralize  the 
effect  of  the  auxiliary  local  Rj  and  exert  a  force  upon  relay  Mg, 
tending  to  attract  its  armature  a^ ;  but  the  latter  is  held  in  the 
position  shown,  against  stop  P„,  by  tlie  retractile  spring  Sg. 

The  armature  a 3  of  i-ehiy  M3  is  carried  from  stop  P3  to  stop 
Oj,  because  the  line  current  is  sufliciently  ])owerful  to  overcome 
retractile  spring  S3,  thus  breaking  the  shunt  and  permitting 
sound<'r  Sg  to  respond. 

Practit'ally,  the  method  of  using  one  receiving  instrument 
having  three  armatures  is  a  very  unsatisfactory  one,  for  the 
reason  that  the  (effective  attraction  of  the  cl(>ctro-magnet  for  any 
one  of  two  or  more  armatures  is  materially  lessened  whenever 
one  of  the  others  is  in  contact,  or  nearly  in  contact,  with  its 
poles. 

The  manner  of  operating  a  register,  or  sounder,  by  closing 
and  breaking  a  shunt,  as  in  the  system  above  described,  would 
render  it  impossible  to  receive  and  record  the  signals  with  accu- 
racy at  any  considerable  degree  of  speed. 


S 
on 

pc 
ba 

CO 


MEKXSTEIX  S   METHODS. 


371 


The  use  of  three  independent  receiving  instruments,  though 
free  from  the  objections  just  mentioned,  docs  not  obviate  the 
difficulties  which  were  inherent  in  the  systems  of  simultime- 
ous  transmission  in  the  same  direction,  invented  by  Stark 
and  Siemens,  in  1855,  and  which  by  the  latter  were  considered 
insurmountable. 

THK    ELECTRO-MOTOQRAPn. 

The  salient  featvi  ^  in  this  discovery  is  the  production  of 
moti«>ii  and  of  sound,  v  the  st3'lus  of  tlie  Bain  telegraph  instru- 
ment, without  the  intervention  of  a  magnet  and  armature.  By 
tlie  motion  thus  })roduced,  any  of  the  ordinary  forms  of  telegraph 
printing  or  sounding  instruments  or  relays  may  be  worked,  thus 
making  it  possible  to  send  messages  by  direct  transmission  over 
tliousanils  of  miles  of  wire,  at  the  highest  speed,  without  rewrit- 
ing, delay,  or  difficulty  of  any  kind. 

More  than  this,  the  apparatus  operates  in  a  highly  effective 
manner  under  the  weakest  electric  currents,  rendering  it  possible 
to  receive  and  transmit  messages  by  currents  so  weak  that  the 
ordinary  magnetic  instruments  fail  to  operate,  or  even  give  an 
indication  of  tlie  passage  of  electricity.  Thus,  when  the  common 
instruments  stand  .still,  owing  to  the  feebleness  of  current,  this 
telegraph  will  be  at  full  work.  The  apparatus  is  shown  in  figs. 
169  ami  170. 

In  fig.  109  A  is  a  lever  pivoted  upon  a  universal  joint  C, 
and  is  provided  at  its  extreme  end  with  a  screw  F,  tipped  with 
l)latina,  resting  upon  a  strip  of  moistened  paper,  which  is  carried 
forward  (in  the  direction  shown  by  the  arrow)  by  the  drum  G. 
This  drum  G  is  continuously  rotated  l)y  clof.'k  work.  The  spring 
S  is  used  for  the  purpose  of  creating  a  pressure  of  the  point  F 
on  the  moistened  paper. 

The  spring  R  is  to  draw  the  lever  to  the  left  and  against  the 
point  X.  L  is  a  main  battery,  K  a  key.  The  zinc  pole  of  the 
battery  is  connected  to  the  point  F,  while  the  carbon  pole  is 
connected  to  the  metallic  drum  G,  through  the  key  K.     Wiien  K 


872 


THE   KI.ECTUO-MOTOdUAl'lI. 


is  olo>!P(l,  tho  clioinicals  witli  wliicli  the  jiaijor  is  saturated  arc 
clocKiiiposcil  l>v  tlif  jiassa.LTt'  of  tho  cuiTctit  tlii'()u;^'li  tlic  ihiikt, 
and  the  lever  rests  against  the  point  X,  closing  tiit^  local  cireuit 
containing  the  sounder  AX  and  local  battery  LB.  If  the  key 
K  is  opened,  the  normal  friction  of  tin;  ])!atina  ])oint  F  upon  tho 
j)apcr  is  so  great  that  the  spring  11  is  insull'icient  to  keep  it 
against  the  point  X,  and  it  is  carried  forwanl  by  tho  rotation  of 
the  drum  to  the  point  1),  where  it  remains  until  the  key  K  is 
agani  closed;  then,  by  the  passage  of  the  current,  the  friction  is 
reduecil  so  as  to  be  impercej)tible,  and  the  spring  R  easily  j)idls 
the  lever  against  X,  where  it  remains  as  long  as  the  current  is 
allowed  to  pass.     As  will  be  seen  from  this  brief  description,  tho 


Fig.  109. 

lever  is  moved  backward  and  forward  by  a  di(T(M-cnco  in  frictions, 
caused  by  tlie  decomposition  of  the  ciii'inicals  (a  solution  of 
chloride  of  sodium  and  pyrogallic  acid),  with  which  the  paper  is 
m(.)istened,  by  the  passage  of  the  current. 

Why  the  paper  becomes  so  extremely  slippery  on  the  pas- 
s;ige  of  the  current,  the  inventor  is  uiial)!e  to  state. 

Tlie  a})])aratus  is  extremely  sensitive,  and  can  be  worked  over 
a  cireuit  of  two  hundred  miles  with  tsvo  cells  of  battery.  Some 
idea  of  its  wonderful  .sensitiveness  may  be  formed  from  the 
stateii'ent  that  by  em[)loying  a  delicate  construction  of  mechan- 
ism and  using  clock  work  to  actuate  the  same,  a  movement  of 
the  lever  has  been  obtained,  sullieieut  to  close  a  local  circuit, 


IS 

liel 
drj 

tlifl 
bej 
fnd 

thJ 


TlIK   I'OLAUIZKD   MOTOGHAPU. 


37;^ 


with  a  current  that  was  incajiable  of  discolorin^'  paper,  mois- 
tened witli  potassic  iodide,  or  of  moving  the  needle  ol"  an  ordi- 
nary galvanometer. 

Unlike  a  magnet,  no  secondary  currents  arc  set  up,  upon 
o))ening  and  closing  the  circuit,  to  delay  the  movements  of  the 
lever;  neither  has  it  cores  to  consume  more  time,  in  charging 
and  discharging,  hut  moves  with  a  maximum  cirect  instantly. 

The  plan  shown  in  flg.  170  is  called  a  polari/2ed  motograjih. 

The  key  K  alternately  connects  the  batteries  A  and  B  to  the 
lever  of  the  motograph,  one  sending  a  positive  and  the  other  a 
negative  current.     The  eui-rent  from  the  battery  A  passes  to  the 


Fig.  no. 

point  X,  thence  through  the  paper  to  the  point  G,  up  through  G 
back  to  the  other  end  of  the  battery  A.  Thus  hydrogeu  is 
generated  on  the  point  F,  which  becomes  slippery,  while  oxygen 
is  generated  on  the  point  G,  which  retains  its  normal  friction; 
hence  the  point  G  is  carried  to  the  right  by  the  rotation  of  the 
drum.  If  the  direction  of  the  current  be  reversed  by  })utting  on 
the  battery  B.  hydrogen  is  generated  fin  the  point  G,  which 
becomes  slippery,  and  oxygen  on  F,  which  retains  its  normal 
friction,  and  the  lever  is  thrown  to  the  left. 

The  diagram  is  arranged  merely  to  illustrate  the  principle  of 
the  invention. 

In  practice,  a  single  battery  and  revei"sing  key  are  used 


374 


TIIK   KI.ECTUO-MOTCXJUAl'II. 


Mr,  Thomas  A.  Edison,  the  inventor  of  the  electro-motogi-apli, 
states  tliat  lu;  has  ;i  machine  in  operation  in  his  lal oratory  con- 
stniotcd  upon  tlio  prineiph;  sliown  in  fig.  lOil,  with  which  he 
lias  succcc(h'(l  ill  repeating  automatic  signals  from  one  circuit 
into  another,  at  tlie  rate  of  oik;  tiiousand  two  h(in(h-ed  words 
per  minute,  an  average  of  six  thousand  lettei-s,  or  twenty-four 
thousaiul  waves  per  minute,  conipelling  the  h>ver  A  (lig.  IfiO) 
to  move  ba('l<\vard  and  forward  from  tlw;  ]K)int  on  tlie  left  to  the 
point  I)  on  the  right  four  ImudnHl  times  per  second. 

By  attaching  an  ink  wliecl  to  the  extremity  of  the  lever, 
opposite  a  coiitiimous  strip  of  paper  moved  l)y  clock  work,  mes- 
sages transmittcil  at  a  spec(|  of  several  hundred  words  per  min- 
ute may  he  recorded  in  iidc  ;  and  hy  attiiehiiig  a  local  circuit  to 
the  ing  i)oints  and  adiling  a  sounder  tlnTcto,  as  shown  in 

thf  ,  tlie  apparatus  may  he  used  as  a  Morse  relay  to  work 

long  hues  of  telegraph. 


CIIAPTKIt  XTI. 


ET.ECTKIC   CALL   UKLLS. 

Thi'",  introduction  of  call  hells  nr  alurrns,  wliioli  liavc  now  bo- 
conu!  of  such  cxteiiHive  application  in  hotels,  factories,  elevators. 
and  wherever  else  their  service  has  lieen  desirable,  or  where  it 
lias  1)ccn  found  convenient  to  employ  electricity  for  operating 
them,  followed,  as  a  matter  of  course,  witli  the  early  introduction 
of  the  electric  telegraph.  The  invention  of  these  instruments 
may,  therefore,  be  said  to  date  as  far  back  as  that  of  the  tele- 
graph itself. 

It  will  rea<lily  be  understood  that,  wliatever  may  be  the  sys- 
tem of  tc^legraphy  employed  for  correspondence  between  places 
distant  from  or  near  to  each  other,  it  is  imj)ortant,  first  of  all,  to 
have  some  means  at  command  by  wliic-h  the  attention  of  the 
correspondent  with  whom  wo  wish  to  conniumicate  may  b(!  ob- 
tained ;  and  this,  of  course,  for  cases  under  consideration,  includes 
the  means  of  prod\icing  a  noise  of  some  kiml  within  his  hearing. 
A  wide  field  has  thus  been  allowed  for  the  exercise  of  man's 
eonstruetive  faculties;  and  tlic  devices  which  have  ])een  succes- 
sively introduced  to  meet  tho  want  have  consequently  been 
exceedingly  numerous.  Their  general  development,  however, 
has  been  very  much  tho  same  as  that  of  the  telegi'aph. 

Professor  Wheatstone,  in  his  earliest  telegraph  experiments, 
made  use  of  a  call  which  was  run  by  clockwork,  the  movement 
of  the  latter  being  controlled  by  the  action  of  an  electro-magnet. 
This  seems  to  have  been  about  the  first  really  practical  instru- 
ment of  the  kind  introduced,  and  even  it  was  not  considered 
altogether  satisfactory  in  its  operation  at  that  time.  Since  then, 
however,  the  apparatus  has  been  so  much  improved  and  simpli- 
fied in  one  way  and  another,  and  the  various  domestic  uses  to 
which  it  lias  been  a]»plied  have  given  rise  to  so  many  different 
forms,  tliat  a  knowledge  of  their  details  becomes  desirable.     We 


37<i 


ki-K(;tiuc  cam,  hki.lh. 


have,  tlieivforc,  tliDuglit  it  wortli  our  wliild  to  dcvoti!  .-i  cliaiitcr  to 
tlio  consideration  of  tlio  moro  important  of  tliis  rluss  of  instni- 

niLMltH. 

Tin-  ]iusli  button  or  key  used  in  short  circuits  scrv<?s  to  close 
the  hitter  ill  a  very  sim[)lo  and  clfecliial  nianncr.  Its  general 
plan  will  bo  made  apparent  by  reference  to  ligs.  171  and   172. 


Pig.  171. 

The  former  shows  the  case  T  of  wood  or  other  insulating  sub- 
stance, within  which  are  secured  the  two  nieUillic  strips  p  and  </, 
one  above  the  other.  In  its  normal  state  the  upper  strij)  is 
separated  from  the  other  by  a  steel  or  s[)iral  spring.  When, 
therefore,  such  a  kev  is  inserted  in  the  circuit  the  latter  remains 
open,  but  may  be  closed  wlieu  desired  by  pressing  upon  the 

P' 


Frj.  172. 

knob  ^/,  which  brings  tlu;  ])oints  y*  and  y  togethei'.  Upon  the 
removal  of  the  pressure  the  circuit  is  again  opeiu-d  by  the  re- 
tractile force  of  the  spring. 

Various  |iatteriis  of  keys  are  made  to  siiiu  the  didercnt  pur- 
poses for  which  they  are  to  be  used.  The  form  .shown  in  fig. 
171  is  th(!  onlinary  one.  Fig.  173  represents  another  form,  used 
for  electric  dojr  belis   in  which  the   circuit  closer  is  contained 


•;^'y^'' 


COMHIVATIOV    KKYS. 


877 


within  a  hollow  in  tho  base,  the  hvlter  IxMng  usually  of  iiiarl)lo, 
and  [iroviiltHl  with  screws  for  securing  it  wherover  desirod. 

FiL'.  17i  is  a  coiivcnifiit  foriu  f'ircDtnliiniuu'  a  iiuiubcr  of  keys 
within  a  small  compass;  eight  jiusii  Ituttons,  corresponding  to 
as  many  distinct  circuits,  arc  arranged  at  c(|ual  distances  around 
a  cyhndrical  case,  within  which  the  connections  lietweea  tlio 


Pi(j.  173.  Fig.  114. 

metallic  strips  and  wires  arc  made.  Each  wire  is  separately 
insulated  l>y  a  silk  covering,  and  the  whole  wound  together  into 
a  single  strand,  where  they  leave  the  case. 

COMIilXATION    KEYS. 

With  the  keys  above  described  it  is  evident  that  the  signals 
last  only  so  long  as  tho  button  is  dep.cssed  by  the  operator;  it 
will  also  be  observed  that  tho  operator  has  no  means  of  knowing 
with  certaint}'  that  a  signal  hiis  been  given,  and  tliat  he  nmst 
therefore  be  still  less  sure  of  its  having  been  noticed.  To  meet 
this  defect,  and  ])rovidc  a  suitable  arrangement  for  every  rcqnirc- 
uicnt,  a  special  combination  is  needed,  such  as  is  shown  in  fig. 


378 


KLKCTRIC   CALL   BELLS. 


176.  This  consists  of  a  case  containing  a  magnetic  needle,  an 
electro-magnet,  and  the  metallic  contact  springs  a  h  and  c  d. 
One  end  of  the  coil  of  the  electro-magnet  J"]  is  attached 
to  the  screw  e,  the  other  to  the  line  wire  by  tlie  insulated  screw 
V.  The  spring  a  h  is  connected  to  the  binding  screw  r  lead- 
ing to  the  battery,  the  other,  c  i/,  to  the  plate  at  e,  by  wliich 
communication  with  the  line  is  made  through  the  coil  of  the 
electro-magnet.  To  the  axis  of  the  magnetic  needle,  A,  is  fas- 
tened a  pm  g,  which  presses  against  the  platinum  contact  r,  when 
the  lower  pole  is  attracted  by  the  electro-magnet,  and  the  needle 


Fill.  176. 

tlius  made  to  take  up  the  position  represented  by  the  dotted 
lines  opposite  which,  on  tlie  cover,  is  the  word  understood, 
or  liere.  The  axis  of  the  needle  is  also  in  electrical  connec- 
tion with  tlio  metallic  back  of  the  instrument,  to  which  are 
attached  the  metallic  plate  p  and  ^  "nding  screw  q,  so  that  all 
three  are  electrically  connected.  Tlic  small  })late  connecting 
with  C,  a  and  r  is  insulated  from  the  back,  and  a  spiral  wire  n  m 
joins  </ with  the  binding  scrcv  e  and  coil  of  E.  In  its  normal 
position  the  p'n  y  rests  against  a  stop  not  shown. 

The  operation  of  the   key   vill  now  be  readily  undcrstoe  1. 


.UM'ARATUS   ]•■(>]{    (ilVIXCr   TIIK   SICXAI-S. 


379 


When  the  knob  B  is  deprcs.sc<l  the  cvirrent  from  C  passes  along  ab 
and  a?  to  e  and  tlirough  the  coil  of  E  to  \',  thence  to  line  L  and  other 
apparuLus,  where  an  audible  or  visible  signal  is  to  Ije  given.  The 
attraction  of  the  needle  A  by  the  electro- magnet  E,  causing  the 
former  to  point  to  the  word  here  on  the  cover,  ena1)les  the  opera- 
tor to  see  that  the  key  has  properly  perfoi'ined  its  ollice.  At  the 
same  time  the  deflection  of  the  needle  brings  the  pin  g  in  contact 
with  r,  so  that  the  current  now  has  a  second  route  through  springs 
r?'aiid^,and  the  needle  remains  deflected  after  the  linger  has  been 
withdrawn  from  B.  Thus  a  continuous  signal  is  given  until  noted 
by  the  person  for  whom  it  is  intended,  who  then  interrujjts  the 
circuit  momentarily  i.y  such  means  as  are  provided  for  the  pur- 
jDose.  With  the  interruption  of  the  circuit  the  needle  returns  to 
its  normal  position,  and  thus  shows  that  the  signal  has  been  re- 
ceived. When  a  vibrating  boll,  to  be  described  jirescntly,  is  used 
for  the  call  apparatus,  a  continuous  to  and  fro  movement  of  the 
needle  takes  place  as  long  as  the  circuit  remains  uninterrupted. 

APPARATUS   FOR   GIVIXCr  THE   SIGNALS. 


The  ordinary  form  of  bells 
used  for  giving  single  taps  is 
shown  in  ligure  176. 

It  consists  of  an  electro-mag- 
net M^r,  ojiposite  whose  poles, 
n  .s,  is  placed  the  armature  with 
its  clap})cr,  l\  The  latter,  in  its 
normal  position,  is  held  back 
from  the  bell  G  by  a  spiral 
spring  attached  to  the  movulile 
upright  d;  which  ici-ves  to  regu- 
late its  tension.  The  stroke  of 
the  aruuiture  is  limited  by  the 
set  screw  r.  Another  form  devis- 
ed by  Brcguet,  in  which  the  ])ro- 
longation  of  the  arnuiture  lever 


Fig.  176. 


380 


ELKCTKIO   CALL   HELLS. 


is  a  ratlier  stiff  spring,  is  shown  in  figure  177.  When  such  an 
aj)paratus  is  placed  in  circuit  with  a  battery  and  one  of  the  push 
button  keys  ah-eady  described,  a  ringing  tap  is  given  ever}' 
time  the  button  is  depressed.  By  coinljining  a  certain  number  of 
taps,  with  proper  intervals  between  them,  it  is  possible  to  com- 


Fig.  111. 

miinicate  words  and  sentences,  and  thus,  besides  being  a  simple 
call,  the  ajjparatus  becomes  a  veritable  tolf^graj)!). 

THE   VIBRATING    BELL. 

Tlie  principle  employed  in  this  arrangement  is  shown  in  figure 
178.  MM  are  the  coils  of  an  electro-magnet,  which  are  so  con- 
nected that  one  end  of  tlu'  wire  leads  to  the  binding  ])ost  B  and 
the  other  to  the  post  G,  To  the  latter  is  also  attached  a  straight 
.'spring  which  carries  the  armature  c,  and,  when  the  current  is  not 


TIIK   VIUIlATINa  BELL. 


3S1 


circulating,  tends  to  keep  it  witlidrawu  from  tlie  jjoIcs  of  tlie 
magnet  and  against  anotlier  spring,  r  ;  this  again  is  in  electrical 
communication  with  the  Linding  po.-t  D,  and  both  B  and  D  are 
connected  respectively  to  A  and  E  by  brass  strips. 

When  such  an  apparatus  is  included  in  the  circuit  with  the 
battery  and  juisli  button,  and  the  button  is  depressed,  tlie  cur- 
rent arriving  at  b  passes  through  the  coils  to  the  post  C  and  arina- 


F^.  178. 

ture  r,  thence  via  the  spring  r  to  ]>ost  E  and  wire  c,  comjilcting 
tlie  circuit.  Tlic  .soft  iron  cores  consequently  become  niagncti/.CMl 
and  attract  the  armature  which  interrujits  the  eurnnit  at  7-,  tliis 
causes  the  cores  to  l)ecomc  demagnetized  again  and  the  armature 
falls  back  again. '"C  the  spring,  when  the  cin;uit  is  once  mon^estab- 
ii.shed  and  an  altraclion  follows  as  before.  Thus  a  rapidly  vibra- 
ting movement  id  set  up  and  continued  as  long  as  the  button  is 
depressed  or  the  circuit  remains  closed  by  the  needle  j)in  before 
referred  to. 


382 


ELECriUC   CALL  llKLLS. 


By  a  slight  modification  of  the  connections  in  the  bell  instru- 
ment the  apparatus  can  be  used  both  as  a  vibrator  and  as  an  in- 
strument to  give  simple  taps.  Tlie  general  plan  is  shown  in  fig. 
179,  in  which  !M  and  e  refer  to  the  same  parts  as  in  the  last.  S 
is  a  switch  which  can  be  turned  on  B  or  E  at  })leasure.  When 
it  is  on  .!']  the  conneciions  are  precisely  the  same  as  those  just 
described  and  the  apparatus  becomes  a  vibrating  instrument ; 
when  turned  on  B  there  is  no  interruption  of  the  current  with 


the  attraction  of  the  armature,  and  the  instrument  simply  re- 
sponds by  single  taps  to  each  closing  of  the  circuit  by  the  push 
button.  The  path  of  the  current,  when  the  switch  is  on  B  and  E, 
is  sufficiently  evident  from  the  figure  without  further  description. 


liQUliLK   HKLLS. 

When  it  is  desirable  to  ])roduce  a  very  loud  sound,  double 
bells  and  double  electro-magnets  are  usually  employed  in  the 
vibrating  apparatus.  Figure  180  represents  an  arrangement  of 
this  kind.  The  current,  arriving  at  the  binding  2)ost  C,  follows 
the  metallic  strips  in  connection  therewith  io  D  and  I)',  thence 
through  the  coils  M  M'  and  strips  11  V,  II'  V  to  the  contact 
springs  II  K'  and  armature  A.  From  A  the  continuation  of  the 
circuit  may  be  traced  by  way  of  15  ami  binding  post  Z,  which 


DOUBLE   BKLLS. 


383 


lead?  hack  to  the  Lattery.  One  of  the  bohbins,  M  for  instance, 
is  wound  so  as  to  produce  a  greater  magnetic  effect  than  that 
produced  by  the  other  W ;  this  causes  the  armature  A  to 
bo  drawn  towards  M  until  tlie  circuit  of  the  hatter  is  broken  at 
E ;  M'  now  acts  alone  until  interrupted  in  turn  by  tlic  break  at 
K',  when  the  same  alternation  is  begun  anew.     Thus,  at  each 


Fig.  180. 

vibration  of  the  armature,  one  of  the  two  bells  is  struck  with 
considerable  violence,  and  the  noise,  with  raj)idly  recurring 
strokes,  is  well  calculated  to  arrest  the  attention. 

In  double  bells  of  this  kind  the  line  circuit  is  never  broken 
by  the  vibrating  armature — the  elToct  of  this  movement  being 
merely  to  shift  the  current  from  one  coil  to  the  other.     This,  in 


384 


KLECTKIC   CALL   UKLLS. 


some  particulur  cases,  is  an  advantage  of  considerable  iiiijiort- 
ance. 

In  general,  the  principle  of  all  vibrating  bells  is  that  of  the 
self-acting  make  and  break;  but,  when  the  contacts  are  rigid 
|K)ints,  the  vibrations  of  the  armature  take  place  only  within 
narrow  limits,  and  the  arrangement  cannot  very  well  be  utilized 
for  ringing  a  bell.  Siemens  has  devised  a  plan,  in  his  dial  in- 
struments, which  answers  the  purpose  much  better,  by  giving 
the  armature  a  greater  range  of  movement ;  but  the  adaptation 
of  this  device  to  the  ringing  of  bells  for  simple  calls  is  a  little 
trouljlesome,  and,  in  fact,  for  general  use,  would  be  altogether 
too  comjilicatcd.  By  far  the  most  jireferable  way  of  obtaining 
the  desired  range  of  stroke  is  that  already  described,  in  which  a 
spring  of  some  kind  forms  part  of  the  path  for  the  current,  and 


Ivl 


01 


Fi'j.  18L 

which,  with  the  attraction  of  the  armature,  follows  the  latter  for 
such  a  distance  as  may  be  required. 

When  one  battery  is  to  serve  for  operating  several  of  the  bells 
above  described,  the  vibrators  cannot  all  bejilaccd  in  one  circuit, 
as  each  one  interrupts  the  circuit  in(lei)endently  of  the  others; 
ami  it  is  impossible,  or  rather  imiiractieable,  to  make  the  arma- 
tures of  tlie  various  instruments  so  that  tliey  will  all  vibrate  in 
exactly  the  same  time,  or  always  be  in  unison. 

The  plan  generally  adopted  for  such  cases  is  shown  in  figure 
181,  where  each  bell,  I,  II,  III,  has  a  se]iarate  conducting  wire 
of  its  own,  as  represented  by  the  numerals  i,  2,  3,  and  a  return 
wire,  L  L,  serves  for  all.  If,  now,  one  of  the  bells  is  operated 
by  the  pressure  of  a  push  button  in  1,  2  or  3,  as  the  case  maybe, 


w 


m 


^•()^'-l^•TKURUl'TI^'(^  ciuci  it  hklls. 


385 


it  acts  -without  in  any  way  interfering  Avitli  tlie  others,  as  they 
MH!  all  quite  independent  of  the  circuit  thus  interrupted. 


SINGLE   BEIJ.S  TO   BK   M'ORKED   WITHOUT   IXTEltHT^PTIXa   THB 

CIHCUIT. 

The  fault  just  noticed  in  connection  with  the  vibrating  arma- 
ture, causing  a  l)reak  at  each  vibration,  may  bo  remedied  in  a 
very  easy  manner  simply  by  causing  the  armature  to  cut  its  owu 
magnet  out  of  circuit  after  each  attraction.  The  principle  works 
very  satisfactorily,  and  will  be  readily  understood  by  reference 
to  figures  182  and  183,  wiiich  represent  two  j^hascs  of  its  appli- 
cation, m  m  arc  the  coils  of  the  electro-magnet ;  a,  the  armature 
to  which  the  clapper  k  is  attached  by  means  of  a  rather  stifE 


tiKjTiriy^ 


X 


-I  H-i»r"-g. 


Mg.  182. 


Fig.  183. 


spring,  and  /  an  elastic  steel  spring,  which  readily  follows  the 
to  and  fro  movement  of  the  armature  for  a  short  distance.  In 
figure  182,  the  armature  itself  forms  part  of  a  shunt  circuit,  by 
Avhich  the  current  is  withdrawn  from  vi  m.  As  will  be  seen,  a 
current  arriving  at  C  passe.-',  through  the  wire  1,  coils  m  m  and 
wire  2  to  the  line  L  ;  the  armature  is  thus  atiracted  to  the  spring 
/,  and  a  second  route  made  for  the  current  by  way  o?  a  c  /.  As 
the  resistance  of  this  route  is  exceedingly  small,  compared  to  that 
of  the  helices,  almost  the  entire  current  jiasses  by  the  new  jiatli, 
and  the  cores  become  demagnetized.  The  retractile  force  of  the 
spring  now  preponderates,  and  the  armature  falls  against  the 
back  stop,  breaking  the  shunt  circuit  on  its  way.  ]?y  this 
means  the  magnetism  of  the  cores  is  again  renewed,  and  a  cou- 


886 


ELKCTHIC   CALL   JiKLLS. 


stant  vibration  kept  up.  In  figure  183,  the  forward  movement 
of  tlie  armature  brings  a  spring  /  against  a  contact  c,  and  forms 
tlie  sliuiit  quite  independent  of  the  armature. 

As  citlicr  of  these  arrangements  does  not  breaic  the  main  cir- 
cuit, any  desired  numl)er  of  tliem  can  be  placi.'d  in  tlie  same  line 
and  worked  witliout  interfering  witli  each  otlier. 

Wlien  the  bell  system  is  to  be  used  for  long  distances,  or  when 
a  very  loud  ringing  is  desired,  for  which  purpose  the  main  line 
current,  as  a  rule,  is  not  sufficient,  a  relay  and  local  battery  arc 


Fi(j.  181. 

generally  used ;  and  with  the  heaviest  apparatus,  requiring  still 
more  power,  the  ringing  is  done  by  means  of  weights. 

Figure  184  represents  an  arrangement  devised  bv  Aubine,  in 
which  a  single  set  of  electro-magnets,  M  M,  serve  both  for  the 
relay  antl  the  call.  A  small  projection  on  the  upper  end  of  the 
armature  </,  when  the  latter  is  in  its  nonnal  position,  supports 
the  lever  ;^,  keeping  it  from  making  contact  with  s]iring  4,  and, 
at  the  same  time,  holding  it  iirmly  against  spring  2.  When  now 
a  current  is  sent  into  the  line,  it  passes  along  the  comiection  1  to 


KI.ECTRIC   Ar>AKM   WITH   KK1.AY3. 


387 


still 


spring  2,  tlioncc  to  lever  3  and  its  connecting  wire  to  spring  / 
and  aniiaturo  «,  and  froia  there  on  tliroagli  the  coils  to  earth. 
This  causes  an  attraction  of  tlie  armature  ;  lever  3  falls  down  ou 
spring  4  and  closes  the  local  circuit,  which  again  results  in  a 
magnetization  of  the  core.  The  arinaturc  is  thus  made  to  vibrate 
in  the  manner  already  described,  and  a  violent  ringing  is  set  u]i, 
whieh  continues  until,  by  pressure  on  the  knob  h,  lever  3  is  agaiu 
raised  and  supported  by  the  armature  projection. 


Fig.  185. 

Figure  185  represents  another  relay  based  upon  similar  prin- 
ciples, and  much  used  in  France.  The  main  line  circuit  is  sufil- 
ciently  ap})areiit  without  further  explanation.  The  local  battery 
0  B  is  inserted  between  the  binding  post  K  and  Z.  From  K  an 
insulated  eojiper  strip  h  h  leads  upward,  and  at  the  top  is  bent  so 
as  to  catch  the  pin  c,  when  the  latter  is  carried  upward  by  the 
spiral  spring  d.  A  ju'ojecting  pin  from  the  armature,  wlien  the 
latter  is  not  attracted,  serves  to  keep  the  rod  F  ^[  depressed. 
With  the  arrival  of  the  line  current  the  armature  is  attracted  and 


888 


ELECTIUC   CAIJi   ]JKI,IA 


tlio  rod  rck'ascd ;  this  allows  the  sjiriiig  d  to  act,  and  close  the 
local  circuit  at  e  h  when  tho  ringing,'  is  commenced.  15y  pressing 
on  tlie  knob  F  the  lower  end  dC  tlio  rod  is  caused  to  engage  with 
the  ])rojocting  armature  pin,  and  the  api)aratus  is  onco  more 
ready  for  another  call. 

SIEMENS  AND   HAI.SKk's  STATION   ATiAUM. 

Tills  is  shown  in  figure  186,  and  consists  of  an  ordinary  relay 
and  bell  magnet,  with  an  automatic  rnako  and  break  arranged 
upon  the  same  principle  as  Siemens'  dial  instrument,  vi  in  are 
tho  coils  of  tho  relay  magnet,  and  1^  and  1^  its  terminal  wires, 
one  of  which  leads  to  line,  tho  other  to  earth.  The  ^jolesonlyof 
tho  bell  magnet  aro  shown  at  M  M,  one  of  its  coils  is  connected 
to  the  binding  post  Z,  the  other  to  a  V  shaped  piece  of  metal, 
termed  tho  shuttle,  which,  in  its  normal  position,  rests  with  ono 
end  against  an  adjustable  screw  in  the  plate  E,  tho  latter  also  iii 
metallic  connection  with  the  relay  lever  a.  Tho  local  battery  is 
joined  to  the  binding  posts  Z  and  K.  When  a  current  is  sent 
into  the  main  line  the  armature  a  is  attracted  and  closes  the  local 
circuit ;  this  charges  the  magnet  M  M  and  actuates  armature  A, 
but  after  passing  a  little  distance  the  long  projecting  arm  on  the 
latter  moves  the  shuttle  against  tho  stop  r  and  breaks  the  local 
circuit ;  the  spring  F,  being  no  longer  restrained,  now  withdraws 
the  armature,  but  in  doing  so  causes  the  shuttle  to  close  the  cir- 
cuit once  more,  and  thus  a  constant  ringing  is  maintained  as  long 
as  the  main  line  is  closed. 


HHKGUETS  ALAUM   OR   CALL. 

With  most  of  the  apparatus  heretofore  described  the  call  or 
alarm  is  only  maintained  for  such  a  period  of  time  as  the  circuit 
may  be  closed  by  the  person  giving  the  signal,  or,  as  witli  the 
arran;j,ement  shown  in  fig.  184,  until  the  messenger  called  stops 
the  ringing  by  depressing  the  knob.  Various  other  combinations 
have  been  suggested  by  Aubine,  Breguet  and  otliers,  by  means 
of  which  a  single  signal  is  made  to  give  any  number  of  taps. 


BKKOUKT.S   ALAint   OK   CALL. 


889 


390 


KLKCTKIC   CAl.li   11K1.L3. 


Brcguct's  arrangement  is  shown  in  figuro  187,  and  its  operation 
may  bo  described  as  follows:  The  line  current  arriving  at  L  in 
consequence  of  the  key  being  depressed,  passes  to  the  contact 
screw  S,  thence  by  way  of  the  lever  C  c,  pivoted  at  C,  through 
the  coils  of  the  olectro-magnct  P]  to  the  armature  a  and  contact 
b  to  earth.  The  armature  is  thus  drawn  forward  for  a  short  dis- 
tance, but  returns  immediately  afterward,  owing  to  the  break  in 
the  circuit  occasioned  by  the  movement,  and  closes  tlio  circuit 
again.  In  this  manner  a  vibratory  motion  is  set  up,  and  with 
each  backward  movement  of  the  armature  the  toothed  wheel  R 


Fi'j.  187. 
is  forced  forward  one  cog,  so  that  the  lever  c  C  is  soon  released 
from  the  pin  g  and  fulls  on  the  contact  screw  d,  placing  the  local 
battery  in  circuit.  The  continued  vibration  of  tlio  armature 
keeps  the  wheel  in  motion,  the  arm  D  is  thus  brougb.t  against 
the  hammer  lever,  and  the  latter  carried  forward  a  certain  dis- 
tance and  tlien  released,  when  the  hammer  strikes  against  the 
bell  with  considerable  force.  With  the  complete  revolution  of 
the  wheel  the  pin  g  engages  with  the  lover  C  c  again,  and  onco 
more  closes  the  main  current. 


COMIIIXATK'V   <>K   f.M.I,   IIKI.T,   .\NI»    JJKI.AY?'. 


391 


COMlUXATItA'   OF   A   !<IN(iI,fc:    (-'Al.I,    BKIJ,    WTl'ir  TU'D  OK  MORK 
HKI.AYS    Foil   SKVKUAI-    J, INKS. 

Wlion  two  or  moro  wires  terminate  at  one  pluco  a  single 
call  bell  may  he  made  to  answer  for  tliem  all,  but  in  such  cases 
each  relay  must  be  [irovided  wilhsotne  arrangement  such  as  the 
rod  F  M  in  fig.  185,  to  .show  on  which  of  the  lines  the  signal  has 
been  sent.  Fig.  188  shows  an  arrangement  of  this  kind.  A  is 
the  electro-magnet  of  tlio  r(,'lay,  who.so  armature  ends  in  a  bent 
hook,  IT,  which  engages  with  the  rod  V  J  ;  m  and  n  are  two 
screws  attached  to  the  upright,  D  Iv,  and  servo  to  limit  the  play 


Fl<j.  188. 

of  the  armature.  This  upright  is  made  iu  two  parts,  insulated 
from  each  other;  the  one  marked  D  is  connected  to  one  pole  of 
the  local  battery  ;  the  other,  K,  is  connected  by  a  wire  S  to  the 
interrupting  spring  '^[  of  the  vibrating  bell  already  described. 
^Yhcn  the  armature  of  the  relay  magnet  is  attracted,  its  upper 
part  is  brought  in  cotitact  with  the  screw  n  and  the  local  circuit 
is  completed,  at  the  same  time  the  attraction  of  the  armature 
releases  the  rod  F  I,  which  is  raised  by  the  action  of  the  spring  d, 
and  thus  shows,  when  attention  Is  called  by  the  bell,  which  line 
has  given  the  signal. 


392 


ELIX^TUIC   CAIJi   BKLLS. 


Each  of  the  several  relays  arc  connected  with  the  bell  magnet 
in  the  manner  shown  in  the  figure,  so  that  there  are  virtually  as 
many  distinct  keys  for  closing  tbe  local  circuit  us  tliero  are  re- 
lays. After  the  call  has  been  observed  tlie  knob  F  is  again  do- 
pressed  wlicn  it  engages  with  the  armature  and  is  held  until 
released  by  another  signal. 

It  is  frequently  desirable  that  the  bell  should  contiime  to  ring 
after  the  main  line  current  has  ceased;  and,  in  order  that  this 
may  be  the  ca^e,  the  upper  pan  of  the  pillar  D  K,  fis.  18y,  is  inade 
the  same  as  its  lower  part,  in  two  soclions,  P  and  Q,  and  each 
insulated  from  the  other.  Two  wires,  S'  Z',  shown  by  the  dotted 
lines,  connect  Q  and  P  respectively  t:>  the  wires  S  and  Z  when, 
therefore,  the  roJ  F  I  is  release.!,  the  action  of  the  spring  t^  brings 
the  small  jjlalinum  tipped  piece  e  against  a sitnilar  contact  on  Q 
and  forms  a  second  closing  of  .t'.ie  local  circuit,  so  that  the  bell 
continues  to  rii]g  until  the  call  has  been  observed  and  the  knob 
depressed. 


SIEMKNS  AKD  UALSKK  3  UELAY   WITH   AXXUXCIATOR   PLATE. 

These  instruments  are  made  in  a  very  perfect  manner,  and  are 
much  used  on  the  German  Fire  Alarm  Telegra|)h.  Fig.  180  rep- 
resents a  perspective,  and  fig.  190  a  sectional  view  of  the  relay, 
which  does  not  diffjr  materially  fro:n  tlic  or  linary  forms,  except 
in  the  addition  of  the  annunciator  disk  and  lever  b  c  i/,  pivoted 
at  c.  The  relays  are  made  for  both  open  and  closed  circuits, 
the  one  represented  being  designed  for  closed  circuits.  The  line 
connections  are  male  at  1  and  2.  K  and  B  connect  with  the 
Morse  recording  ajiparatus,  while  the  alarm  bell  is  joined  to  A 
and  the  metallic  piece  "\v^  V.  In  its  normal  state  the  lever  of 
the  disk  is  held  in  a  horiz  )nt:d  position  by  the  hook  on  the 
lever  a  a,  but  with  any  interruption  of  the  main  circuit  the  ar- 
mature is  drawn  off  by  the  action  of  s[)ring/  and  releases  the 
disk,  wliicli  is  now  raised  to  a  vertical  position  by  the  weight  h  ; 
ihis  closes  the  call  circuit  at  t  at  t  le  same  time  tiuxt  the  armature 
a  a,  falling  on  t.ie  back  contact  v/t,  actuates  the  Morse  recording 


KELAY   "VVITU  ANNL'XCIATUK   I'J.ATE, 


893 


Fig.   ISU. 


894 


KLKCTRIC   CALI^   J3KI.LS. 


TTf* 


Fig,  190. 


CLOCK  WORK  ALARM. 


395 


instrument.  Wlien  the  automatic  vibratinj^  bell  is  used  tlio 
ringing  is  kept  up  until  the  lever  and  disk  are  returned  Xo 
their  horizontal  position  by  the  operator. 


Fi'g.  l!)(i. 


CLOCK   'WORK  Af.ARM. 

Those  oalls  arc  constructed  in  various  ways,  to  suit  the  dilTerent 
purposes  for  which  they  are  to  serve;  in  some  the  hamincr  is 
operated  by  weights  or  S[)rings,  and  made  to  give  a  single  stmki' 
for  cac'h  impulse  of  current  sent  into  the  line;  in  others,  tlu' 
strokes  are  reiicated  a  certain  nunilier  of  times;  or  again,  the 
ringing  is  continuous;  but  in  all  cases  the  current  has  only  one 
function  to  perform,  that  of  releasing  tlie  train  of  clock  work. 
This  is  usually  accomplished  by  tlie  action  of  an  electro-magni't 
on  its  armature,  and  tlie  weights  or  springs  cause  tlie  signalling. 
An  important  and  much  used  ap[)aratus  of  this  kind  is  that  of 
llagendorlf 's,  which  gives  but  a  single  stroke  for  each  depression 


39G 


ELECTKIC   CALL   BELLS. 


of  the  signaling  key,  and  which  is  therefore  preferable  to  the 
vibrating  "bells  for  many  purposes,  especially  in  places  where  the 
rattle  oi  the  latter  is  likely  to  be  more  or  less  annoying. 

The  use  of  weights  or  springs  for  causing  the  separate  bell  taps 
is  also  to  be  preferred  to  the  tapping  from  a  clapper  canied  by 
the  armature  lever,  as  with  the  latter  arrangement,  owing  to  an 
occasional  tardy  withdrawal  of  the  hammer,  the  signals  are  not 
always  very  distinct. 


Fig.   i;H.  Fig.  l'J2. 

Figures  191  to  194,  inclusive,  show  the  principal  parts  of 
Hagcndorfl's  apparatus;  the  letters  refer  to  the  same  parts  in 
each  figure. 

Figure  191  gives  an  interior  view  of  the  works.  B  B  is  p.irt 
of  the  brass  frame  to  the  back  of  wliich  is  attached  an  electro- 
magnet M  ;  fig.  19;]  rcprcaetits  the  inside  view  of  the  same  plate. 
The  wheel  I,  fig.  191,  is  loose  on  the  axis  n'  and  carries  a  disk 


CLOCK   M-OKIC   ALARM. 


897 


g,  better  sliown  in  fignro  192  :  this  is  provided  with  a  detent  S 
and  spring  F  F,  whicii  ])resses  the  former  into  the  teelii  of  the 
ratchet  wlieel  /,  thus  preventing  tlie  hitter,  as  well  as  tlu;  wheel 
H,  which  is  fastene<l  to  it,  from  turning  in  the  direction  indicated 
l)y  the  arrow  without  at  the  same  time  causing  the  wheel  1  to 
tnrn  with  it.  The  wheel  R  is  jirovided  with  radial  ])ius  wliich 
catcli  in  a  chain  passing  over  it  and  attached  to  the  weight  P, 


Fiij.  193. 

fig.  194,  the  pins  serving  to  ]irevont  the  chain  from  slijipiug.  As 
will  he  seeu,  the  ratchet  allows  the  wheel  Z  and  K  \n  ho  freely 
turned  in  a  direction  op])osite  that  indicated  hy  the  arrow;  tliis 
riiiscs  the  weight  P,  which,  in  descending  again,  sets  the  whole 
train  in  motion,  wheel  1  communicating  its  movement  to  wheel 
11,  and  the  latter,  in  turn,  acting  on  axis  g'  and  stop  lever/ 
connected  to  it. 


398 


ELECTKIC   CALL   HELLS. 


The  wheel  11,  fig.  193,  can-ies  near  its  circumference  eight  ot 
ten  projecting  pins,  A  A,  wliicli  raise  tlie  ana  1  on  the  axis  k.  A 
powci'ful  spring,  S,  surrounding  tliis  axis  and  in  communication 
with  it  and  with  the  frame  of  the  aj)})aratus,  tends  continually  to 
keep  the  arm  depressed.  When,  therefore,  the  latter  is  raised  hy 
tho  revolution  of  the  wheel  the  spring  is  suhject  to  considorahle 
tension,  and  as  soon  as  a  pin  jiasses  from  under  the  arm,  causes 

■".■■;  f--"'*f  u*.  ■'■■■*  ■'^'     ■    '  ':•'■ 


Fig.  VH. 

the  latter  to  descend,  and  the  hammer  K,  attached  1o  the  axis  k 
\n-  the  arm  «,  strikes  the  hell  with  .some  violence.  The  pin  m 
.serves  to  limit  the  play  of  the  arm  n. 

Figure  191  represents  the  rehiy  armature  attracted.  When 
no  current  pa.sses  in  the  coils  of  the  matrnet  the  armatiin!  re- 
mains down  and  the  train  work  is  arrested  hy  the  arm/,  which 
eatches  in  the  escapement  d'  ce'.  Tlie  ends  e  e  of  the  escapement 
art-!  so  made  that  the  back  one  e  is  a  little  nearer  than  the  front 


^ 


CLOCK   WUKK  ALARM. 


399 


one  e'  to  tlie  plate  B  B,  but  tlio  two  .iro  attached  to  one  ])iece, 
arid  move  togcitlier  with  any  movement  of  tlie  armature.  Tlio 
operation  of  the  apjtaratus  will  now  he  readily  understooil. 
When  a  current  is  sent  into  the  line  the  armature  of  m.agnet  M 
is  attracted,  the  front  point  e'  of  the  escapement,  fig.  191,  is 
moved  to  the  left,  and  the  arm/ is  carried  forward  by  the  action 
of  the  weight  on  the  train  work  to  e,  and  as  soon  as  the  circuit 
is  broken  e  moves  toward  the  back  B  B,  and  the  arm  makes 
one  comjdete  revolution,  when  it  is  stop])('d  again  by  e^.  Simul- 
taneously with  this  movement  the  i)ins  h  h  ]iass  under  the  arm 
Z,  and  the  hammer  strikes  against  the  bell,  making  one  tap  for 
each  make  and  break  in  tlie  circuit 


CHArTKR    XT  1 1. 


TIIK  ELKCTKIC  J.KillT. 


WlIEN"  the  terminal  -wires  of  a  hattery  containing  a  number  of 
cells  are  brouLrlit  togctlier,  and  then  separated  slightly,  there 
results,  as  is  well  kufnvn,  an  intense,  hright  light  between  tlicni, 
and  to  this,  on  account  of  its  curved  form,  tlic  name  electric 
arc  has  been  given.  If  tlie  circuit  is  not  immediately  broken, 
the  ends  of  the  wires  rapidly  become  heated,  and,  in  a  very  short 
time,  melt  and  drop  oIl  in  glowing  globules.  Portions  arc  even 
volatilized  and  pass  off  as  vapor,  wliose  color  varies  with  the 
kind  of  metals  eniplo3-ed.  and  with  the  medium  \n  which  the 
experiment  is  made.  The  distance  between  the  cuds  conse- 
(piently  increases  rapidly,  and  a  point  is  soon  reached  at  wliich 
tlie  light  is  interrupted,  the  electro-motive  force  of  tlie  battery 
being  then  no  longer  sulhcicnt  to  maintain  a  current  against  the 
opposing  resistance.  If,  however,  tlic  wires  are  again  brought 
together,  and  then  separated  as  before,  the  arc  is  once  more 
established,  but,  as  we  have  just  seen,  it  will  last  onl}'  for  the 
very  short  time  during  which  the  electro-motive  force  is  suffi- 
cient to  overcome  the  resistance  between  the  points. 

When  two  pointed  jjieces  of  hard,  conducting  carbon  arc  used 
for  tlie  terminals,  as  sliown  in  fig.  195,  the  light  becomes  of 
dazzling  brightness,  too  intense,  by  far,  if  the  numl)er  of  cells  is 
considerable,  to  be  carelessly  regarded  by  the  unprotected  eye 
alone.  By  viewing  it  through  coloi-ed  glass,  however,  or  liy 
projecting  an  image  of  it  upon  a  screen,  it  may  be  studied 
without  danger. 

As  the  nund)cr  of  cells  is  augmentcil,  the  light  becomes  not 
oidy  more  intense,  but  the  arc  may  be  materially  lengthened, 
while  its  temperature,  at  the  same  time,  is  still  further  increased. 

In  the  brilliant  experiments  of  Davy,  which  were  performed 
at  the  beginning  of  the  present  century,  with  some  2,000  cells  of 


11 


t 


TKMl'EKATURE   UF  THE   ELECTIUC   AIIO. 


401 


buttery,  and  wliicli  were  the  first  that  were  made  on  an  extended 
seale,  an  arc  of  four  iiiclies  in  length  was  obtained  in  tlie  open 
air,  and  in  vaeuo  it  increased  to  seven  inches.  Since  then,  more 
powerful  elements,  and  greater  numbers  have  been  employed, 
and  the  resulting  eirects  have  been  on  a  corresponding  scale. 

In  temperature  as  well  as  brightness,  the  voltaic  arc  exceeds 
all  other  artificial  sources  of  lieat ;  by  its  means  the  most  refrac- 
tory substances  are  fused  and  volatilized,  including  even  the 
diamond  itself,  which  Despretz  succeeded  in  reducing  to  vapor. 


Fi'j.  195. 

As  the  liglit  continues,  the  ])ositive  carbon  is  found  to  waste 
away  much  more  raj)idly  than  the  negative — a  fact  lirst  observed 
by  Sillimun — and  although  the  latter  is  first  to  become  heated, 
its  temperature  in  the  end  is  less  than  that  of  the  former,  as  may 
be  seen  when  the  light  is  interrupted,  the  positive  carbon  then 
continuing  to  glow  for  sonic  time  after  the  negative  h.'is  become 
dark.  In  addition  to  this,  it  is  also  found  that  i)articles  of  the 
carbon  are  forcibly  detached  from  the  jiencils  and  carried  across 
the  arc.     This  transport  of  particles  can  be  rendered  visible  to  a 


402 


TUK    KLKCTRIO   LIGHT. 


large  nnmUer  of  persons  at  on(^  tiino  by  tlii'owiiii^  an  image  of 
the  liealed  jioints  upon  a  screen,  with  tlu;  aid  of  a  h;iis.  On 
watcliing  the  imago  for  a  few  miMiitcs,  incan(l(!scent  partides 
will  be  observed  traversing  tlie  length  of  the  are,  sometimes  in 
one  direetion  and  sometimes  in  the  other,  the  ])revailiiig  diree- 
tion  being,  however,  tliat  of  tlie  positive  current.  Tiiis  eireum- 
stiinee,  wliich  apjiears  to  be  conneeted  with  tlie  higher  tempera- 
ture of  tlie  ])ositivo  terminal,  explains  the  ditfereni:e  between 
the  foiTns  assumed  by  the  two  carbons.     The  point  of  the  posi- 


Foj.  H)6. 


live  carbon  becomes  concave,  while  the  negative  remains  pointed, 
and,  as  stated  above,  wears  away  less  rap'Uy.  In  vacuo  the 
diflferencc  is  still  more  marked.  A  kind  of  cone  then  grows  upon 
the  negative  carbon,  while  a  conical  cavity  is  formed  iu  the 
jiositive. 

Fig.  106  shows  a  convenient  ajiparatus  for  experimenting 
with  the  light  in  vacuo  and  in  various  gases.  It  consists  of  a 
bell  shaped  receiver  of  glass,  provided  with  three  tubular  open- 
ings, two,  d  and  o,  opposite  each  other,  and  the  third,  i,  on  top. 


a 
ai 
d( 
th 
\\ 


DUBOSCQ.S   I{Er,l'l,.\'li»I{. 


408 


To  the  latter  is  littcil  u  st(i])  fork  and  tn!)0,  wliicii.  serve  for 
coimoctiiig  tlie  apparatus  with  tlio  air  j)Uinp,  and  also  for  intro- 
ducing various  gases  when  necessary.  The  other  two  serve  to 
hring  tlie  two  oleetrodes  opposite  cacli  other,  inside  of  tlie 
reeeiver,  and  are  provided  with  tightly  fitting  caps  thmugli 
wiiicii  the  electrodes  pass.  Tiic  one  over  the  opening  c  allow.s 
the  electrode  n  to  li(i  pns]ie(l  in  or  out  at  plea.sure,  ami  eai'ries. 
hesides,  a  .scale  o,  by  means  of  which  the  length  of  the  arc  may 
readily  bo  ascertained.  A  ground  glass  j)lute,  clamped  to  the 
bottom  of  tiic  receiver,  completes  the  details  for  rendering  the 
a{)paratus  air  tight. 

AVith  the  arrangement  shown  in  figs.  195  and  196,  the  liglit, 
as  we  have  already  seen,  is  .«oon  extinguished,  owing  to  the 
increased  di.stance  between  the  points  by  the  burning  or  wasting 
away  of  the  carbons ;  consecpiently,  when  wo  reijuire  to  use  it 
continuously  for  any  considerubU;  length  of  time,  it  becomes 
necessary  to  cmjiloy  some  mechanical  means  fen*  keeping  the 
pencils  at  the  right  distance  apart,  or  for  bringing  them  together 
again  automatically,  if  from  any  chance  cause  they  should 
become  separate(l  sufficiently  to  car.se  th(!  light  to  go  out.  A 
great  many  forms  of  apparatus  have  been  ilevised  for  this  pur- 
l>ose,  some  exceedingly  simple,  and  others  more  or  less  compli- 
cated. 

Fig.  197  shows  a  form  of  lamp  devised  by  Duboscn,  and  oper- 
ated by  the  combined  action  of  the  current  and  a  system  of 
wheel  work,  driven  by  a  spring  in  connection  with  one  of  the 
wheels. 

On  a  circular  brass  ])late  A,  is  mounted  a  metallic  tube  B,  to 
which  is  attached  the  binding  post  C.  A  m(>tallic  rod  D,  sliding 
in  this  tul)e,  carries  at  its  t<)[)  the  arm  E,  to  which  is  also  attached 
ii  rod  and  socket  for  holding  the  upper  carbon.  This  rod  is 
arranged  to  slide  in  the  arm  K,  so  that  it  may  be  moved  up  or 
<lowii  for  a  liniit(>d  distance,  and  is  held  tightly  in  any  position 
that  may  be  given  to  it.  The  lower  end  of  tlie  rod  D  is  pro- 
vided with  a  rack  F,  which  engages  with  the  wheel  G,  and  the 
latter  again  is  jircssed  on  to  the  axis  of  another  wheel  II,  and 


404 


THK  ELECTIUO  LIGHT. 


firmly  hM  in  jilace  l)y  friotioa  Within  a  barrel  connected  with 
wlurl  11  tlicre  is  a  ])i)\verf\il  si)rinj,',  which  serves  as  the  niotivo 
force  for  actuatini^  the  ine('hanisin  oi!  the  lanij).  A  (liiiil)le  rack 
J,  tenniuatiug  above  iu  the  rod  (),  which  i)iusscs  tlu'ough  an 


Fig.  197. 

insnlatinjf  j.niidc  in  the  cover,  and  is  ])rovided  with  a  Roclsct  for 
holding  the  lower  carlxm,  engaged  on  one  side  with  the  wheel 
IT,  and  on  the  other  with  the  axis  of  wheel  K.  This  wheel,  iii 
like  manner,  engages  with  the  ])inion  of  wheel  L,  better  shown 


I 


DUBOSOgS   UKGUI.ATOK. 


405 


in  fi>(.  198,  and  tlie  latter  u^'uiii,  with  an  endless  screw  M  <>n 
the  i>n)l(in^'-ati(>n  of  the  axis,  eurryinj,'  th(3  co<r  wiii-i'l  iV  and 
lly  X.  An  <'lectr()-iiia;_nH't  P,  consisting  of  a  hollow  iron  tulie, 
with  its  liclix  of  insnlated  coiiper  wire,  is  jilaccd  in  the  Ikiso  of 
the  lamp  ;  and  ono  end  of  the  wire  of  the  helix:  is  connected  to 
Llie  liimling  post  V,  insulated  frf)ni  the  cover,  tlie  other  to  the 
lower  end  of  tlie  rack.T,  which  moves  up  and  down  in  the  liollow 
of  tlM;  core.     A  circular  piece  of  iron  Q,  attached  to  the  Itent 


Fi'j.  198. 

lever  R  S  T,  serves  as  an  armature  to  the  magnet,  and  when 
attracted  by  the  latter,  causes  the  pallet  of  the  supplementary 
lover  U,  which  is  controlled  hy  the  long  lever  R  S  T,  to  catch  in 
the  wheel  K,  and  thus  arrest  its  motion  and  that  of  the  train  of 
wheels  with  which  it  is  in  connection.  There  is  also  a  ])in  or 
rod  in  coiniection  with  the  apparatus,  that  can  he  i)ushed  in  from 
the  outside,  and  made  to  start  or  stop  the  train  w^ork  when 
desired. 

When  the  lam[)  is  to  be  uscmI,  the  rod  1)  is  raised.    This  causes 


406 


THE   ELECTRIC   LIGHT. 


the  wheels  G  and  II  to  revolve,  and  tlms  at  the  same  time 
lowers  the  rod  0,  so  that  the  carbons  can  be  inserted.  If 
allowed  to  act  now,  the  spring  witiiin  the  barrel  connected  with 
II  will  cause  the  carlxMis  to  approach  and  touch  each  other. 
The  battery  can  then  he  connected ;  the  positive  pole  to  the 
])0.st  V,  the  negative  to  C.  With  the  passage  of  the  current 
through  the  ctjil  surrounding  the  core,  the  armature  will  be 
attracted  and  the  train  thus  locked ;  but  the  points  may  be  properly 
separated  again  by  raising  the  rod  carrying  the  upper  carbon, 
and  the  light  will  then  shine  out  in  all  its  brilliancy.  As  the 
carbons  burn  away  the  curi'cnt  necessarily  becomes  weaker,  on 
account  of  the  incnvised  resistance  of  the  arc,  and  a  time  soon 
comes  when  the  magnet  is  no  longer  strong  enough  to  retain  the 
armature.  The  n^tractile  spring  then  prevails,  and  releases  the 
wheel  N,  and  thus  aljows  the  spring  in  the  barrel  of  II  to  act 
and  bring  the  points  once  more  near  each  other.  With  the 
decrease  in  the  distance  between  the  ])oints,  the  current  becomes 
stronger  and  the  armature  is  again  attracted.  A  moment  more,  it 
is  again  rclcascMl  ;uid  again  attracted,  and  so  its  position  con- 
tinues to  vary  from  time  to  time  with  the  changes  in  the  strength 
of  the  current.  It  therefore  becomes  possible,  by  the  use  of  tlie 
lamp,  to  maintain  the  light  for  a  very  long  time  without  inter- 
ru})ti<)n.  As  will  be  observed,  the  diameter  of  wheel  II  is 
double  that  of  wheel  (1,  and  consequently  the  carbon  connected 
with  the  holder  0  moves  through  twice  the  distance  of  that  in 
the  upper  holder.  The  object  of  this  is  to  coin])ensatc  for  the 
more  rapid  wasting  away  of  the  positive  carbon,  which,  as  has 
b(>cn  found,  consumes  about  twice  as  fast  as  the  negative.  The 
use  of  wheels  of  different  diameters  thus  furnishes  the  means  for 
keeping  the  light  at  a  given  point,  which  is  a  matter  of  consider- 
ai)l<'  iuipor':ince  in  almost  all  of  tln^  uses  to  whi(;h  it  is  a[)plied; 
and  when  a  reflector  is  usnl,  is  absohitely  neeessarv,  as  other- 
wise it  would  be  all  but  inijuxssible  to  keep  the  light  properly 
focused. 

Fig.  199  shows  another  form  of  lani|),  (levis(>d  bv  Foucault, 
in  this  there  are  two  svstenis  of  wln'cl  wor 


one  for  l)ringing  the 


rOUCAULT'S  BEGULATOR. 


407 


^^<M 


Fig.  199. 


408 


THE   ELECTRIC   LIGHT. 


carbons  together  and  the  other  for  separating  them,  and  it  is  prin- 
cipally in  the  addition  of  this  last  arrangonicut  that  the  lamp 
differs  from  that  of  Duboscq,  there  being,  in  the  latter  form,  no 
provision  for  automatically  relighting  the  lamj)  in  ease  it  should 
accidentally  go  out.  L'  is  a  barrel  driven  by  a  spring  inclosed 
within  it,  and  driving  several  intermediate  wheels,  which  trans- 
mit its  motion  to  fly  o.  L  is  the  second  barrel,  driven  by  a 
stronger  spring,  and  driving  in  like  niainier  the  fly  o'.  The 
racks  which  carry  the  carbons  work  with  toothed  wheels  attached 
to  the  liarrel  L',  the  wheel  for  the  positive  carbon  having  double 
the  diameter  of  the  other,  the  same  as  in  the  Duboscq  lamp. 
The  current  enters  at  the  binding  screw  C,  on  the  base  of  the 
apijaratus,  traverses  the  coil  of  the  electro-magnet  E,  and  passes 
through  the  wheel  W(jrk  to  the  rack  D,  which  carries  the  positive 
carbon.  From  the  positive  carbon  it  passes  through  the  voltaic 
arc  to  the  negative  carbon,  and  thence,  through  the  support  H, 
to  the  binding  screw  connected  with  the  negative  pole  of  the 
battery.  When  the  armature  F  descends  toward  the  magnet, 
the  other  arm  of  tlic  lever  F  >'  is  raised,  and  this  movement  is 
resisted  by  the  spiral  spring  R,  which,  however,  is  not  attached 
to  the  lever  in  (juestion,  but  to  the  end  of  another  lever,  pressing 
on  its  upper  side  and  movable  about  the  point  X.  The  lower 
side  of  this  lever  is  curved,  so  that  its  point  of  contact  with  the 
first  lever  changes,  giving  the  spring  greater  or  less  leverage, 
according  to  the  strength  of  the  current  In  virtue  of  this 
arrangement,  which  is  due  to  Robert  Ilouilin,  the  armature, 
instead  of  being  placed  in  one  or  the  other  of  two  positions,  as 
in  the  ordinary  forms  of  apparatus,  has  its  i)osition  accurately 
regulated,  according  to  the  strength  of  the  current  The  anchor 
T  Ms  rigidly  connected  with  the  lever  F  P,  and  follows  its  oscil- 
lation:- If  the  current  becomes  too  weak,  t);c  head  t  moves  to 
the  right,  sto2)S  the  (iy  o'  and  releases  o,  which  accordingly 
revolves,  and  the  carbons  are  moved  forward.  If  the  current 
becomes  too  strong,  o  is  stopped,  o'  is  relcaseil,  and  the  carbons 
are  drawn  back.  When  the  anchor  T  t  is  exactly  vertical,  !;•  tth 
flies  are  arrested,  and  the  carbons  remain  stationary.    The  curva- 


FARMERS   AUTOMATIC   LAMP, 


409 


I 


tiiro  of  tlie  Icvor  on  vvliich  the  spring  acts  heing  very  slight,  the 
oscilhitions  of  the  armature  and  anclior  arc  small,  and  very 
slight  changes  in  the  strength  of  the  current  and  brilliancy  of 
the  light  are  immediately  corrected. 

Mr.  Hart,  of  Edinburgh,  Scotland,  has  invented  a  simple 
lamj),  in  which  the  weight  of  the  rod  in  which  the  carbon  is 
fixed  supplies  the  jdace  of  the  clcjck  work  in  the  lain])  ju.«t  de- 
scribed, and  an  electro-magnet  lets  it  descend,  or  locks  it,  as  the 
carbons  are  consumed. 

-  -  Mr.  Farmer,  of  Newport,  R.  I.,  has  also  invented  an  automatic 
lamp,  containing  but  little  train  work,  and  whose  action  is  con- 
trolled by  a  regulator  or  relay,  consisting  of  an  axial  magnet, 
the  coils  of  which  are  placed  cither  directly  in  the  main  circuit 
or  in  a  branch  of  the  same,  and  a  delicately  poised  lever,  frona 
one  end  of  which  the  a.\is  bar  of  the  coil  is  suspendeil.  The 
action  of  the  current,  when  too  strong,  tips  the  bar  in  one  direo 
tion,  and  when  too  weak  a  retractile  spring  tips  it  in  the  other. 
It  is  the  employment  of  this  relay  to  operate  the  mechanism  of 
the  lamp,  through  the  intervention  of  loeal  or  branch  circuits, 
whi.'h  constitutes  the  jirineipal  dilference  betwtH'u  tliis  and  Jiux^t 
of  t'fc  other  forms  of  lamps  now  in  u.se.  The  train  of  wheel 
WLi'k,  driven  by  a  spring,  tends  to  cause  the  carbons  to  approach 
.,  .i'  oiher,  but  the  motion  is  arrested  if  the  armature  of  a  small 
■■l>-it<  magnet,  forming  ])art  i,(  the  apparatus,  is  attracted.  The 
tii'.i  g  iiar  <jf  the  regulati)r  closes  the  local  circuit  of  this  releas- 
ing magnet  wdiencver  the  current  is  of  the  proper  strength,  but 
as  soon  aa  the  current  weakens,  by  the  b\irning  away  of  the 
points,  the  ri'tractilc  spring  of  the  regulator  cau.^cs  the  lever  to 
open  the  branch  circuit  of  the  releasing  magnet,  and  the  arma- 
ture of  the  latter  then  allow.s  the  train  to  move.  The  carbons, 
consequently,  approach  each  other  until  the  main  current  again 
beciinesof  such  strengtii  that  tiie  regidatiM"  ('loses  the  branch 
circuit  of  the  detaining  magnet,  and  thus,  once  more,  stops  the 
motion  of  the  train. 

\V  lien  the  ]»oint3  run  into  actual  contact,  after  the  arc  has 
been  broken,  the  light  is  ayain  established  bv  a  third  electro- 


410 


THE   ELECTRIC    LIGHT. 


magnet,  also  in  the  main  circuit,  wliicli  witlulraws  the  lower  car- 
bon from  contact  with  tlie  up])cr,  and  holds  it  in  ]iosition  nntil 
the  arc  is  again  hroken.  The  movement  of  the  carbon  holdei-s 
is  caused  by  ih^  action  of  two  screws  so  geared  together  that  one 
pencil,  the  p>  .-  aoves  twice  as  ra])idly  as  the  other. 

There  are,  be  ,  conveniences  attached  to  each  of  the  car- 
bon pcncil-liolders,  so  that  they  can  be  disengaged  from  the 
screws  and  moved  independently  to  any  required  position  at 
pleasure.  The  holders,  also,  admit  of  separate  adjustments  on 
a  vertic^J  axis,  so  that  by  this  means  the  carbons  can  be  placed 
in  a  perpendicular  line,  one  above  the  other.  The  spring  iloes 
not  need  rewinding  oftener  than  new  carbons  are  supplied,  and 
the  performance  of  the  lamp  is  very  satisfactory.  It  has  Ixjcn 
run  for  hours  when  required,  and  no  reason  exists  why  it  should 
not  run  continuously  until  the  jjcncils  are  consumed,  provided 
it  be  jiroperly  adjusted  at  first. 

AVithin  the  last  two  years  a  new  form  of  electric  light  appa- 
ratus has  been  introduced  in  Fraiu'c  and  elsewhere,  which,  from 
the  ri'iiiarkal)lc  proj)erties  that  have  been  attributed  to  it,  has 
attracted  a  great  deal  of  attention.  '^I'lie  invention  is  due  to  M. 
JablochkolT,  a  liussian  engineer,  and  is  kimwu  as  Jabloehkofl's 
caudle.  It  consists  of  two  carbons  placed  si<le  by  sidi>,  and  S(>p- 
arate(l  by  an  insulating  and  fusible,  substance.  No  cloeiv  work 
whatever  is  rcMpiired,  and  the  light  is  very  soft  and  steady 
Fig.  200  shows  the  arrangement  as  originally  designed.  '^I'he 
carbons  «,  /;,  some  four  inches  in  length  and  one  fpiarter  of 
an  inch  square,  are  imbcddcil  in  an  insulating  sulistanee  <: ; 
the   carbon  slips   being  also  separati'd    from  each   ollu'i"  some 


three  sixteenths  of  an  inch 


aiK 


1  t 


u!  wnoi(!  nioi 


dded  into  the 


si 


la 


pe 


jf  a  candle.     In  ord(>r  to  facilitate  tla^  <'arlv  act 


ion  o 


f  tl 


le 
111 


current,  a  small  ])i(>co  of  carbon,  about  the  si/e  of  the  lend  of 
ordinary  leail  pencil,  is  })laccd  across  the  top  of  the  electrodes. 
A  series  of  experiments  with  candles  of  this  ileseri|itioii  were 
carri(Ml  out  at  Chatham  soiiu!  time  since,  and,  it  is  slated,  the 
]K>wer  then  obtained  was  some  lifty  j)er  cent,  greater  than  that 
obtained  ])reviously  from  the  recognized  electric  light 


JABLOCIIKOFF  S  CANDLE. 


411 


I 


Since  then,  M.  Jiibloclikoff  has  twice  modified  tliis  arrangu- 
ment,  each  modification  ])cing  attended  witli  success  heyond  tiiat 
obtained  by  the  preceding.  His  first  proceeding  was  to  divest 
tlie  carbons  of  tlicir  outer  covering,  leaving  notliing  but  the 
carl)on  shjw  a,  }>  (lig.  201),  and  tlie  intervening  substance,  kaoHne, 
c.  Each  carbon  is  iixol  in  a  small  bra.ss  tube  d,  e,  the  lower 
portions  of  which  arc  left  vacant,  so  that  they  may  fit  over  two 
metal  pin.s,  attachcil  to  which  are  the  wires  from  the  magneto 
macliine.  These  tubes  are  insulated  one  from  the  other,  and 
the  whole  bound  together  by  a  band  of  insulating  material/.' 

The  latest  modification  embraces  the  removal  of  the  carbons 


H 

Fig.  201. 


and  the  replacement  of  them  by  a  carbon  jiaste,  a  sort  of  prim- 
ing, the  object  of  which  is  to  reduce  the  resi.stanee  which  the 
kaolinc,  when  cold,  intci'iioscs  to  the  ])assage  of  the  current. 
With  this  arrangement  a  .splendid  band  of  light,  constant,  soft 
and  steady,  is  obtained. 

Tlie  principi.l  ailvantages  of  the  candU;  appear  to  be  due  to 
the  fact  that  it  is  lUMthcr  dazzling  nor  blazing,  and  does  not, 
tliercl'oi'c,  surround  the  various  objects  illiuninatcd  with  the 
disagreeable  h.'i/e  and  trhastlv  shadows  that  are  observed  when 


tl 


10  onniKirN' 


•l.vl 


ric 


hiilit  If 


is.'d.     It   is,  1 


lowcvi'i',  somcw 


hat 


more  cxpcnsuc,  liut,  as  a  <'orn[ii'nsation,   is  said  to  allow  ol  a 


412 


THE   ELECTRIC   LIGHT. 


greater  subdivision  of  tlie  onrrent — as  many  as  fifty  lights  liaving 
been  maintained  from  a  single  source  by  its  use. 

A  novelty  in  electric  lamps  lias  just  been  brought  out  by  Mr. 
Wallace,  and,  we  learn,  will  soon  be  placed  in  the  market  at  a 
veiy  low  figure.  It  consists  principally  of  a  substantial  metallic 
frame  and  an  electro-magnet.  There  are  two  slides  in  the  frame, 
each  capable  of  holding,  in  a  hori:^outal  position,  the  two  carbons, 
which  are  made  in  tlie  foi-m  of  plates,  twelve  inches  long  by 
two  and  a  half  wide,  and  half  an  inch  thick.  The  upper  and 
lower  parts  of  the  framework  are  insulated  from  each  other,  and 
in  electrical  connection  with  two  binding  posts,  on  the  upjior 
part,  serving  to  connect  them  with  the  magneto  machine.  The 
electro-magnet,  through  whose  helices  the  main  cuiTent  circu- 
lates, is  placed  in  the  centre  of  the  frame  above  the  carbons,  and, 
by  its  action  on  an  armature,  serves  to  separate  the  ujipcr  carljon 
from  the  lower,  to  any  distiuice  desired. 

When  the  lanip  is  joined  with  a  magneto  machine  by  means 
of  the  binding  posts  and  conducting  wires,  the  circuit  is  com- 
jileted  through  the  carbons,  whicli  touch  eacli  other,  and  the 
armature  is  attracted,  thus  separating  and  holding  them  apart  so 
long  as  the  current  is  maintained.  The  light  burns  toward  the 
opposite  end  from  which  it  started,  then  changes  and  burns 
back  again,  always  burning  toward  the  place  where  the  carbons 
are  nearest.  If,  from  any  cause,  the  light  goes  out,  the  circuit  is 
broken,  and,  of  couree,  the  electro-magnet  ceases  to  act  But 
the  instant  the  upper  carbon  falls  the  circuit  is  again  closed,  and 
the  carbons  are  once  more  separated  and  relighted. 

The  advantages  of  this  lamp  are  tliat  it  contains  no  coml)ina- 
tion  of  wheels  or  springs,  and,  consequently,  there  is  n(j  winding 
up  of  the  apjiaratus  to  look  after.  The  carbons,  again,  arc  so  large 
that  they  will  last  for  ten  nights,  of  ten  hours  eacli,  and  tlio 
lamp  requires  no  care  except  for  their  renewal,  '^riie  practical 
disadvantage  that  suggests  itself  is  its  lack  of  means  for  main- 
taining the  light  at  a  given  point,  so  as  to  use  it  in  connection 
with  a  reflector. 

Figs.  202  and  203  show  two  forms  of  the  Bru.^h  electric  lamp,  as 


AIAGNETO-ELKCTKIO   MACIIINKS. 


418 


mamifiictnird  Ity  the  Tolcfri-aph  Supply  Compuny,  of  Cleveland. 
J''ig.  202  is  u  huiigiiig  lamp,  intended  for  factory  use  ;  fig.  203 
an  adjustable  table  lamp. 

There  are  also  a  great  many  other  lamps,  such  as  SeiTin's, 
Browning's,  Siemens's,  etc.,  and  all  of  which  are  more  or  less 
employed  when  it  is  desired  to  maintain  the  constancy  of  the 
light  for  long  continuous  working ;  but  the  apparatus  we  have 
just  described  contain  most  of  the  princii)al  characteristics  and 
conveniences  embodied  in  these,  and  it  will,  therefore,  be  un- 
necessary to  give  more  attention  to  this  j^art  of  the  subject  at 
l)resent. 

Instead  of  the  battery,  whose  employment  for  light  purposes 
is  now  almost  exclusively  confined  to  the  illustration  of  lecture- 
room  experiments,  and  physical  demonstrations  in  class  rooms, 
or  to  the  production  of  luminous  effects  in  theatrical  exhibitions 
— places  where  it  is  seldom  convenient  to  employ  a  steam  en- 
gine—  dynamo-electric  nuiehines  are  now  almost  universally 
used,  and  their  advantages  over  the  battery  are  very  marked  in 
a  great  many  particulars.  Of  late  years,  dynamo  machines  have 
also  been  extensively  introduced  in  electro-plating  establish- 
ments, to  take  the  place  of  batteries,  but  in  such  cases  their  con- 
struction is  ccmsiderably  modified,  in  order  to  adapt  thena  to 
this  particular  kind  of  work.  As  ordinarily  constructed  for 
light  purposes,  the  machines  would  have  an  electro-motive  force 
far  too  high  for  plating,  where,  as  a  general  thing,  two  or  three 
volts  are  all  that  are  re(piired. 

Largo  magnoet-electric  machines,  for  light  purposes,  a])pear 
to  have  beiMi  first  suggested  by  Professor  Nollet,  of  ]irussels,  in 
1850,  but  since  then  a  great  many  modifications  and  improve- 
ments have  been  introduced,  so  that  the  machines  of  to-dav, 
although  depending  for  tlieir  action,  like  the  earlier  ones,  upon 
the  same  inductive  princi^tle  by  which  mechanical  force  is  trans- 
formed into  electricity,  are  nevertheless  far  superior  to  them, 
both  as  regards  economy  and  efi'ectiveness  when  in  action. 

Fig.  20-t  represents  one  of  the  first  forms  of  these  machines  as 
constructed  by  Holmes,  of  London,  an<l  the  Coinpagnie  V  Alliance, 


414 


TllK   ELKCTUIC   LlCillT. 


I 


Fig.  202. 


I 


IIKUSH'S  AUTOMATIC   UEUULATOHS. 


416 


I 


416 


TIIK   EI.ECTUIC   LIGHT. 


of  Paris,  and  wliich  at  one  time  promised  to  become  of  vt-ry 
extensive  ujiplicatioii  for  liglit-lionse  purposes. 

In  tliis  muchino  tiicre  are  figlit  rows  of  compound  liorseshoc 
magnets  lixed  symnietrically  around  a  cast  iron  frame.  They  are 
so  arranged  that  the  opposite  poles  always  succeed  each  other, 
both  in  each  row  and  in  each  circular  set.  There  are  also  seven 
of  these  circular  sets,  with  six  intervening  spaces.  Six  bronze 
wheels,  mounted  on  one  central  axis,  revolve  in  these  intervals, 


Fig.  204. 

the  axis  being  driven  by  steam  power,  transmitted  by  a  pulley 
and  belt  The  speed  of  rotation  is  usually  350  revolutions  of  the 
axis  i)er  minute.  Each  of  the  six  bronze  wheels  carries,  at  its 
circumference,  sixteen  coils,  corresponding  to  the  niimbcrof  jioles 
in  each  circular  set.  The  core  of  each  coil  is  a  cleft  tube  of  soft 
iron,  this  form  h;iving  been  found  jicenliarly  favorable  to  raj)id 
demacrnetization.  Each  core  has  its  magnetism  reversed  sixteen 
times  in  each  revolution,  by  the  inllucnee  of  the  sixteen  succes- 


l1 


SI  KMENH  S   A KMATURK. 


117 


sivc^  ]iiiirs(it'  ]>oles  liotwccii  '.vliich  it  jiasscs :  and  tlio  same  iinmlit'i- 
of  i:uiT('ii1s,  ill  altcniatt'ly  ti|i|i()sii('  ilircctiuiis,  arc  generated  in 
the  foils.  Tli;'  cdil.s  ran  lie  coiiiicclcd  in  difld'cnt  \\a\s,  acciU'd- 
ing  as  gi'cat  olectro-niotivc  l'i>rce  or  small  resistance  is  recpiired. 
'Plit;  positive  ends  an-  connccte(l  witli  the  axis  of  the  macliine, 
wliicli  thus  serves  as  the  positive  electrode;  and  a  eonecntrio 
eylinder,  well  insnlated  from  it,  is  employed  as  the  ncLfativo 
electrode. 

In  I'So-i  Siemens  devised  a  very  eU'eetive  arnxalun^,  which  has 
since  been  much  employed  hy  othci-  maMufaetiirers  in  dill'erent 
Tonus  of  machines.  The  principal  advantage  of  this  armature 
residts  from  its  occupying  hut  little  space  for  rotation.  Conse- 
quentl}-,  it  can  be  kept  in  a  very  strong  magnetic  lield ;  at  the 
same  time  also  its  form  renders  it  well  adaiited  for  rotation.  It 
consists  of  a  jieculiarly  sliaped  electro-magnet,  such  a.s  wouM  be 
formed  liy  cutting  two  wide  and  deep  longitudinal  gn^oves  oppo- 
site each  other  in  a  eylindi'ical  bar  of  iron,  and  then  continuing 
tliem  around  the  ends.  'I'he  wire  is  wound  lengthwise*  around 
the  core  in  the  groo\e,  like  thread  upon  a  shuttle,  and  l)rass  caps, 
))rovide(l  with  axes  and  a  pidhy,  ai'c  then  screwed  on  to  tlie  end.s 
of  the  magnet.  When  this  armature  is  mounted  between  the 
poles  of  a  series  of  jiermanont  horseshoe  magnc^ts  and  rotated 
rapidly,  very  strong  euri'cnts  are  produced.  The  two  ends  of 
tlie  wire  are  connected  with  a  commutator,  formed  by  fastening 
two  semicircular  pieces  of  ])rass  to  an  ivoi'v  ringon  tlie  a.xi.s  and 
sjirings  bearing  upon  tluve  brass  pieces,  and  in  metallic  con- 
nection with  the  binding  [^ists  of  the  apparatus,  supply  the  means 
for  collecting  and  comlueting  awa\'  the  I'leetricity  j>roduceil  in 
the  wire  coils. 

By  employing  tw 
of  the  property  whi 
.lughcr  degree  of  magnetism  than  sttrl.  and  eon.<e([uently,  there- 
fore, of  itw  ca])ability  of  producing  stronger  currents  by  induc- 
tion in  movable  coils  within  its  lield.  ^[r.  Wilde,  of  >ranehester, 
England,  has  succeeded  in  constructing  \'ery  enei'getic  machines, 
and  which  arc  well  adaptcil  for  producing  the  electric  light. 


o  of  these  armatures  and  taking  ad\anta!.;"e 
eh  soft    iron   possesses  of  receiving  a  much 


418 


TlIK    KM'XTIilC    I.KillT. 


'Plio  n]i|>aratus  in  ivjility  consists  of  two  macliinoa  comMncd  in 
oiu'.  Tlic  curiviit  from  one  of  tlio  Sicnu-ns's  ariruitun's,  pro- 
tliU'od  l)y  its  ra[ii(l  rotation  in  the  strou<^  mairnctio  liuld  of  a  scries 
of  [icrmancnt  magnets,  is  employed  to  cliarge  a  large  and  power- 
fnl  electro-magnet,  between  whose  poles  tlie  second  arniatnre  is 
made  to  revolve,  and  the  current  from  tli(!  latter  is  utilized  for 
the  liglit. 

Twi>  armatures  for  the  eleetro-magnet  are  sometimes  furnished 


Pig.  205, 

with  the  m.'icliine,  one  with  wire  coils  for  the  jiroduetion  of  cur- 
rents of  rather  high  electro-motive  force,  to  be  used  for  light 
puq)oses  alone,  and  the  other  with  coils  of  sheet  copper  strips, 
which  give  currents  of  less  electro-motive  force,  but  more  esi)e- 
cially  adapted  for  j)lating.  With  the  interchangeable  armatures, 
which  are  di'iven  by  belts  running  on  pulleys  on  their  axis,  the 
machines  can  be  used  either  for  lighting  or  for  ])lating  at  pleas- 
ure, and  this,  iu  some  particular  cases,  is  a  very  desirable  feature. 


r 


LADliS    DVNAMOKMX'TKIC    MACHINK 


•Hil 


Niimrnuis  otlicr  iimcliines  arc  ('oii>^tnu't('(l  willi  intorcliaiigoabic 
ai'iiialuri's,  on  tlic  same  |ilaii  ami  fnr  the  sann'  jdirpusc. 

.\nntlirr  form  of  iiia^riicto  apparatus  is  that,  ktiowii,  from  tlic 
naiiic  of  its  inventor,  as  tin-  Ladil  iiiai'liiiic.  This  was  lirst 
j)ul)liclv  cxhiliiti'il  at  the  Paris  Hxposition  of  18(i7.  It  is 
sliowii  ill  li,L^  20."),  and,  as  will  be  seen,  employs,  like  the  Wilde 
niacliiiic,  two  Sicincns's  armatures,  l)ut  it  dilTers  from  tiic  latter 
princi])ally  in  not  lia\in,t:  any  pi'i'inancnt  niaLnu^ts  wliatcvci'  to 
eliarjijc  the  armature  whicli  supplies  the  horizontal  Hold  coils  B  B. 
Two  Ion;.'  flat  pieces  of  soft  iron  are  plaeeil  within  these  coils  .ind 
attached  to  the  iron  castings  or  pole  pi(!ces  .MM,  XX,  which  are 
turned  out  just  large  enough  for  the  armatures  to  fit  inside 
of  them  and  rotate  without  touching.  Thick  strips  of  l)rass 
or  other  nonmagnetic  metal  are  also  jilaeed  between  the  upper 
and  lower  castings  .\[  and  .X,  to  keep  them  separate  from  each 
other,  ami  thus  subject  the  armatures  between  them  to  the  full 
f(jr(;e  <jf  their  inducti\e  action. 

The  connections  of  the  coils  are  such  as  to  jtroducc  opposite 
jiolarities  in  M  and  X:  and  the  armature  at  the  left  of  tiie  ma- 
chine supplies  the  field  coils,  while  that  at  the  i-ight  furnishes  the 
current  for  the  light. 

One  of  the  most  remarkable  jiroperties  of  these  machines  is 
that  by  virtue  of  which  they  become  capable  of  producing  exceed- 
ingly ])owerful  currents  from  the  smallest  beginnings;  tin;  simple 
reactive  eJTectof  the  very  slight  residual  magnetism  that  remains 
in  th(!  cores  after  they  have  once  been  charged  being,  in  fact, 
all  that  is  required,  on  revolving  the  armatures,  for  their  produc- 
tion ;  and  to  operate  a  new  machine,  it  is  only  necessary  to  plai'e 
it  in  such  a  way  that  the  armatures  will  stand  in  the  magnetic 
meridian,  and  then  cause  the  one  which  supj)lies  the  iield  coils 
to  rotate  rapidly.  This,  of  course,  causes  the  convolutions  of 
wir(!  surrounding  the  latter  to  cut  through  the  lines  of  ftn'ee  due 
to  terresti'ial  magnetism,  and  jiroduw's  iii  them  electrical  cuirrents 
of  greater  or  less  magnitude,  depending  upon  their  velocity  of 
rotation,  wdiich,  on  traversing  the  larger  coils  B  B,  render  the 
cores  and  jiole    jiiec-es  M   X  slightly  magnetic.     The  reactive 


420 


TUK    KLECTRIC   LIUIIT. 


ofTect  of  the  magnetism  in  tlie  pole  pieces  on  the  armature  is 
thus  added  to  tliat  produced  by  the  earth's  ma.irnetism,  and  an  in- 
creased current  flows  into  tlie  liel<l  coils.  A  <j,re:it('r  de.irreo  of  luaiz;- 
netism  is  con-c(|ucntly  produced  in  the  pole  pieces,  which  causes 
the  latter  to  react  once  more  on  the  armatures,  and  the  result  of 
which  is  a  C'ori'espondin;:;  increase  in  the  current,  and  increased 
magnetism.  By  this  means,  tlierefore,  tlio  curi'ent,  in  an  exceed- 
ingly brief  interval  of  time,  increases  from  nothing  to  a  maxi- 
mum of  strength,  at  which  it  remains  practic;Uly  constant  for  a 
uniform  velocity  of  armature  rotation.  It  is  usually  h(>tter,  how- 
ever, and  much  more  convenient  in  charging  a  machine  for  the 
first  tune,  to  use  the  current  from  a  battery,  nv  from  anotlier 
machine  til i\'ady  charged,  than  to  depend  alone,  for  this  ellect, 
upon  terrestrial  magnetism. 

The  machines  thus  far  descriiied  furiiisli  only  momentary 
currents  of  varying  strength  and  [<olarity.  If  currents  of  but  ono 
direction  are  rccpiired,  these  intermittent  currents  must  be  recti- 
fied, as  v;e  have  already  seen,  Ijy  means  of  a  commutator,  and 
this  cau.ses  a  diminution  in  the  strength  of  current,  and  is  fre- 
([ucntly  accom|ianied  by  the  ]>roduction  of  spark.s.  !Mi'.  /.  ,1. 
Gramme  has,  however,  invented  a.  machine  in  which  these  oiijcc;- 
tions  are  not  met  with,  as  the  current  obtained  from  it  Hows 
contiimously,  and  in  one  direction  only. 

The  magnetic  lidd  in  this,  as  in  other  machines,  is  created  by 
a  powerful  magnet,  of  .;uch  a  sha[>e  tiiat  its  poles  confront  each 
other,  iind  its  cliaractcristic  feature,  thercifore,  lies  wholly  in  tlie 
construction  of  tlie  armature.  This  consists  of  a  ring  of  soft 
iron,  siu'roiinded  by  an  ciidless  coil  of  wire,  and  is  rigidly 
attached  to  an  a.vis,  so  that  it  can  bo  made  to  revolve;  on(! 
half  of  the  ring  being  nmler  the  inHuence  of  the  north  pole,  and 
the  other  under  that  of  the  south  jxile  of  the  magnet. 

•  As  the  ring  revolves,  every  poiMion  of  it  changes  position  in 
the  magnetic  field  ;  but  no  current  is  develo[H'd  in  the  wire,  con- 
sidered as  a  whole,  as  the  latter  entirely  surrounds  tlu;  ring,  and 
tlio  magnetic  state  of  this,  as  a  whole,  remains  unchang(Ml.  A 
point  on  the  ring  considered  In'  itself,  however,  changes  polarity 


GKAilMKS   MACHINE. 


421 


twice  (luring  every  rcvolutioi).  As  it  recedes  from  one  i»ole,  it 
generates  in  tlie  surrouiuliiig  \vii'e  :in  olectro-inotivi!  force,  tlic 
same  as  tliat  generated  wlien  it  approaches  the  other  pole,  and 
the  two  e]ectro-moti\'e  foi-ccs,  conseciuentl}',  ojipose  each  oflier, 
but  wlienevei'  an  external  conductor  is  provided  between  them, 
they  unite  and  ])roduce  a  ciuTent. 

In  ])ractice,  the  ring  consists  of  a  l)un<lle  of  soft  iron  wire,  and 
the  helix  is  made  in  sections,  each  one  of  wliicli  is  c<inncctcd  to 
its  neighbor,  and  also  to  a  strip  of  brass  forming  the  means  of 
connecting  with  the  external  circuit.  During  a  revolution,  and 
when  the  eleotro-motix'c  forces  of  opposite  sections  are  at  a  max- 
imum, the  corresponding  brass  strijis  touch  a  couple  (jf  metallic 


Fig.  206. 

springs,  and  thus  make  connection  with  the  extevMa.l  conductor. 
The  peculiar  construction  of  the  ring  will  be  seen  !;y  referring  to 
fig.  20t),  wln-rc  Sfcvcral  sections  of  the  wireB  l";  arc  shown  upon 
the  ring  A.  The  iigure  also  shows  the  way  in  which  v'oniiecitiou 
is  made  with  the  brass  sti'ij)s  R. 

A  coi'.vejiient  form  of  the  Granuue  machine,  constructed 
esi)ecially  for  the  laboratory  and  lecture  t;d)le,  is  shown  in 
iig  207.' 

At  tho  jM'Csent  time  electric  light  machines  and  machines  for 
plating  purposes  aui  made  by  numerous  manufacturers  in  this 
country;   but,  perhaps,  by   none  on   a  scale   so  large  as  that 


422 


THK   KLKC'l'KK!   MGHT. 


iisoiiia,  Cdimi.      This 


carried  on  by  !^[essrs,  Wallace  k  Sdus,  of  ^V 

iirni  l)egaii  tlie  t'onstructioii  ut  tlieso  iiKU'liincs  fur  tlic,  market  in 

tlio  sprint^  of  1.S75,  and  .<iiu'o  that  tiino  there  is  liardi)"  any  fi)rm 

ot  Jiiagiieto  iiuicliiuo  tliat  has  not  been  built  ami  tested  at  their 

works. 

The  macliine  which  they  finally  decideil  n[)on  manufacturing, 
as  possessing  th(>  greatest  merit,  is  the  invention  of  !Moses  (i. 
Farmer,  formei'ly  of  Boston,  but  now  and  iov  the  last  three  years 
elcetrician  at  the  Government  Torpedo  Station,  at  Newport,  K.  1. 


Fig.  207. 

Tliis  machine,  which  has  ])een  somewliat  moditied  and  im- 
proved upon  from  time  to  time  by  Mr.  William  WaUace,  is,  in 
many  respects,  unlike  any  of  tlie  other  forms  that  we  liavo  con- 
sidered. It  consists  of  two  large  electro-magnets,  an  armature, 
two  commutators  and  four  brushes,  the  latter  forming  ])art  of 
tlio  circuit,  and  sci'ving,  when  the  macliiiu!  is  in  operation,  to 
collect  the  currents  gen<M'ated  in  the  armature  coils.  The  two 
magnets  are  mounted  upoiL  a  cast  iron  frame,  similac  to  that  of 


FARMKKrf   DVXA.MO-ELECTRIO   MACHINE. 


423 


a  latlio,  ami  are  inail(3  to  faeo  eacli.  other,  while  the  annature, 
wliicli  consists  of  an  iron  casting  of  varying  diauictci-,  according 
to  the  si/(!  of  tilt!  machine,  is  mounlcil  n[ion  a  shaft,  ami  placed 
between  the  magnets.  Tlio  shaft  also  cari'ics  pulleys  at  eat.'ii  of 
its  ends,  and  is  made  to  rest  in  hearings  in  the  yokes  of  the 
electro-magnets.  The  arinatnre  disk  ctirries  on  each  side,  and 
near  its  periphery,  twenty-live  wedge  sliapecl  projections,  of 
whicli  there  arc  fifty  in  all,  that  face  the  poles  of  the  electro- 
magnets, and  on  which  coils  of  wire  an;  placed.  Tlii^  terminals 
of  these  coils  are  joined  togetlicr,  and  a  wire,  coiniected  with  the 
jnnctions,  leads  to  the  coimnutator,  sitnated  on  tin;  same  side  of 
the  ])late — all  tli(!  coils  on  one  side  connecting  with  one  eoin- 
mntator  and  all  on  the  opposite  side  with  the  other. 

The  connnntators  are  jilaced  upon  the  sliaft,  l)et\v<>cn  the  legs 
of  the  two  magnets,  and  consist  of  wood  or  other  im  ire  dnrahle 
insnlating  snhstance,  on  which  stri})S  of  brass,  connecting  with 
the  wires  from  the  armatnre  coils,  are  secured  The  cimnections 
of  the  machine  are  so  arranged  that  when  e\-ternal  circuit, 

which  may  consist  of  the  light  a[iparatus  or  depositing  vats  with 
their  leading  wires,  is  completed,  the  armature  and  lield  of  force 
coils  are  combinc(l  with  it  in  one — an  arrangement  for  winch  Mr. 
Farmer  obtained  a  patent  in  1872,  and  which,  when  the  external 
resistance  is  low,  is  of  very  gi'cat  advantage. 

The  eight  inch  machine,  so  called  from  the  length  of  its  electro- 
magnet, and  which  is  the  one  most  commoidy  employed,  will  pro- 
duce two  lights  of  about  two  thousand  candle  power  each,  and 
is  so  arrangctl  that  tlm  two  may  be  (jombined  in  one  if  dt'sired. 
It  weighs  si.x:  Inuidred  ])ounds,  and  re([uires  to  drive  it  about  one 
horse  power  for  every  twelvti  hundred  candle  light. 

The  machines  made  by  Messrs.  Wallace  &  Sons  weigh  from 
one,  hundre(l  ar.d twenty-live  to  three  thousand  pounds  each,  and 
are  ca[)able  of  j)rodueing  alight  enual  to  that  of  from  one  thou- 
sand to  forty  thousand  candles.  Sonii!  of  them  will  e\en  maintain 
the  are  with  the  carbons  three  and  a  half  inches  apart.  l''ig.  208 
shows  another  form  of  the  light  machine,  as  construct(Ml  by  the 
Telegraph  Supply  Co.,  of  Cleveland,  on  a  i)lan  devised  by  Mr.  C. 


i2i 


TlIK   KLECTKIO  LIGHT. 


BRrSHS   DYXAMO-ELKCTUIG   MACHINE. 


425 


F.  Brush.  'J'liero  arc  two  marked  difTercnccs  ])etwL'cu  this  and 
other  luachinos,  the  fii'st  of  wliiili  coi'sists  in  tlic  peculiar  iiietliod 
adopted  for  winding  llio  ariiialure;  tl:e  latter  is  coiii|ioseil  of  a 
ring  or  endless  band  of  iron,  l)ut  instead  t)f  havitig  a  uniform 
cross  section,  like  that  of  the  Gramme  machines,  is  jirovided  with 
grooves  or  depressions  whoso  direction  is  at  rijiht  aimles  to  its 
magnetic  axis  or  length.  These  grooves,  which  may  be  of  any 
suitable  nund)er,  according  to  the  uses  for  -wduchthe  machine  is 
designed,  are  wound  full  of  insidated  co])))er  wire.  The  advan- 
tage of  winding  the  wire  in  grooves  or  depressions  in  the  arma- 
ture is  twofold;  first,  the  projecting  portions  of  the  armature 
between  the  sections  of  wire  may  be  made  to  revolve  very  close 
to  the  ])o]es  of  the  magnets  from  which  the  magnetic  force  is 
derived,  liy  this  means  the  iniUictive  force  of  the  magnets  is 
utilized  to  a  much  greater  extent  than  is  possible  in  the  case  of 
annular  armatures  as  onbiiarily  used,  which  are  entirely  covered 
with  wire  and  cannot,  therefore,  be  brought  very  near  the  mag- 
nets :  second,  owing  to  the  exposure  of  a  very  considerable  por- 
tion of  the  armature  to  the  atmosphere,  the  heat,  which  is  always 
develojted  by  the  rapidly  succeeding  magnetizations  and  demag- 
nctizati<uis  of  armatures  in  motion,  is  ra]>idl3'dissi})ated  by  radi- 
ation an<l  convection,  lu  the  case  of  armatures  entirely  covered 
with  wire  the  cseajie  of  the  heat  is  very  slow,  so  that  they  must 
run  at  a  comparatively  low  rate  of  speed,  with  corresponding 
ellect,  in  order  to  jirevent  injurious  heating.  The  second  dilTer- 
cnc-e  lies  in  the  manner  of  connt'eting  the  armature  coils  to  the 
eonimutalor,  this  being  such  that  only  the  jiarticular  coils  which 
contribute  to  the  production  of  tlu;  current  are  in  circuit  at  once. 
During  th(;  time  they  are  pas.sing  through  the  neutral  points  in 
the  magnetic  field  they  are  cut  out  one  after  the  other,  and  thus, 
while  idle,  do  not  tend  to  weaken  the  elTects  of  the  machine  by 
afTording  a  jiath  to  divert  the  current  generated  in  the  active 
gections  from  its  pro]  ler  channel. 

It  woulil  b(\  an  interesting  matter,  if  the  eflieieiiey  of  all  the 
dijrcrent  iiiaehines  cm])ln\  <•(!  in  the  jiroduclion  of  the  electrio 
light  could  be  obtained  and  published,  so  as  to  be  reailily  avail- 


426 


THE   KLKCTRIO   LIGHT. 


able.  A  general  comparison  could  then  1)o  made  wliicli  would,  in 
a  measure,  settle  the  ever-recurring  question  in  regard  to  tlio 
puiieriority  of  this  or  that  machine.  Undoubtedly,  this  infor- 
mation exists  for  many  of  the  machines,  as  nnniennis  measure- 
ments of  them  have  heen  made  hy  different  expcriiaenters,  but 
the  results  have  in  most  cases  never  been  nuide  |iulilic,  and  arc, 
therefore,  to  be  found  only  in  the  hands  of  tlio  individual 
exjierimenters  themselves.  It  may  be  stated,  however,  from 
such  information  as  we  have  found  available,  that  theamountof 
energy  obtainable  as  electricity  from  the  best  machines  jirobably 
does  not  exceed,  or  if  so,  only  in  a  slight  dcgi-ce,  two  thirds  that 
of  the  mechanical  force  rctj^uircd  to  drive  them. 

The  expense  of  maintaining  the  electric  light  is  much  less 
than  that  incurred  by  the  employment  of  any  of  the  ordinary 
mctliods  of  illumination.  Mr.  Fai-mer  states  tliat  -whci-e  a  Luvo 
amount  of  light,  say  from  live  thousand  to  ten  thousand  eandlo 
light,  is  rc([uircd,  it  can  be  produced  from  a  suitable  machine  at 
the  rate  of  one  thousand  candle  light  per  horse  ])owi'r;  but, 
smaller  amounts — say  two  hundred  to  three  hundi'cil  candle 
light — are  relatively  more  expensive,  ])rol)ably  about  one  half 
horse  power  for  tw(j  hundred  to  two  hundred  and  lifty  candle 
light 

This  i.>  much  more  economical  than  when  ])roduced  from  any 
of  the  ordinary  forms  of  galvanic  battery.  One  iiorso  ]io\vcr 
may  be  reckoneil  as  costing  from  tw(j  to  six  cents  ])cr  hour, 
which  would  give  the  cost  of  ten  thousand  candle  light  as  sixty 
cents  per  hour,  simply  for  power.  Of  course  some  other  items, 
such  as  oil,  attendance,  interest  and  depreciation,  also  cost  of 
carbons  consumed,  would  increase  this  amount  somewhat,  but 
even  at  twice  or  three  times  this  cost  it  is  still  much  less  expen- 
sive than  gas  light  at  three  eamllc  light  to  the  cubic  foot  per  hour, 
at  $2.50  per  thousand  for  gas. 

The  dilliculty  of  procuring  carbons  that  would  burn  uni- 
formly has  been  a  source  of  a  great  deal  of  annovancc.  If  tlie 
carbon  is  taken  just  as  it  (^omes  from  tlu^  gas  retorts  and  sawed 
into  shape,  it  is  found  to  contain  many  impurities,  and,  -vvhea 


BRUSH  S  IMPHOVKI)   OAIIHOXS. 


427 


biirnin;;,  will  frequently  split  and  large  pieces  drop  ofT.  If  it  is 
first  j>aiverized  and  tiieii  pi'cssed  int(j  shape,  as  is  done  for  but- 
terv  plates,  dilTiculties  of  one  form  or  another  still  appear,  ami 
tlic  Ujiig  voad  of  trial  and  failure  lias  generally  had  to  be  pretty 
well  trodden  over  by  all  who  have  given  this  part  of  the  sub- 
ject niueh  attention.  Mr.  Wallace,  who  has  studied  it  very 
clo.sely,  has,  we  believe,  succeeded  in  producing  v(M-y  satisfactory 
carbons,  but  we  are,  a.s  yet,  unacquainted  with  the  process. 

The  best  illuminating  effect  appears  to  be  produced  from  thin 
carbon  pencils,  but  it  lui,;  heretofore  been  found  imprai;ti- 
cable  to  use  such  pencils,  on  account  of  their  high  resistance 
aiul  the  rapid  consumptiim  of  material  due  to  the  action  of  the 
air  on  their  highly  heated  cuds.  ^fr.  Brush  has  sought  to  ob- 
viate these  diflicultics,  and  at  the  same  time  improve  the  illumin- 
ating power  of  the  light,  by  the  admixture  of  different  foreign 
substances  with  the  carbon  and  by  surrounding  the  stick  either 
mechanically  or  by  electro-plating  widi  various  metals.  By  this 
nu^ins  a  free  and  ready  conductor  is  afl'ord('(l  for  the  current 
and  a  good  coinieetion  between  the  carbon  and  its  holder  securcvl. 
while  the  employment  of  longer  and  thinner  p(>neils  is  also  ren- 
dered jiractieable,  and  there  is  little  or  no  liability  to  breakage. 

Ill  operation  the  intense  heat  of  the  arc  melts  and  disperses  the 
covering  of  the  carbon  sticks  at  their  opposing  points  and  lor  a 
pro[)er  distance  beyond,  but  no  farther.  The  balance  of  tin?  car- 
bons is  entirely  preserved,  while  as  fast  as  tlu^y  are  burneil, 
just  so  fast  will  their  covering  bo  removed,  leaving  the  carbons 
exposed. 

Tlu^  subdivi-sion  of  the  light  is  another  of  the  problems  that 
have  occu[)ied  the  attention  of  inventors  a  great  deal.  JS'o  one 
doubts  that  the  division  can  bo  effected,  but  to  do  this  in  a 
simple  manner,  and  offer  to  the  public  a  cheap  and  ])raetieal 
device  for  the  jiurpose,  has  not  been  an  ea-<y  task  It  would 
a])pear,  from  ,«oine  of  the  latest  experiments  made  at  the  works 
of  Messr.s.  Wallaee  Si  Suns,  that  there  is  scarcely  any  limit  to 
tlu!  nunilierof  suliilivisioiis  that  eiui  be  maile,  ami,  to  a  (H'r- 
tain  extent,  most  of  the  machines  are  now  constructed  to  give 


428 


TIIK   EI.KCTUIO    l.lCiri'. 


sepfiratc  liglits.  One  form  of  coustructidii  of  tlio  Bnisli  nni- 
cliiiie  is  capable  of  ])ro(liiciiii^  four  indciicinlcnt  lii^Iits.  i>f  J!, 000 
candle  powers  oat'li, 

The  best  means,  however,  for  obtaining-  a  niimlior  of  lij^lita 
from  a  single  source  consists  in  tiie  emj)loyinent  of  thin  strips 
of  jilatinum  or  iridium,  whose  tcm]M'raturo  is  raised  by  the 
jiassage  of  the  current  to  a  ])oint  oidy  slightly  below  the  melting 
])oint  of  these  metals.  A\''hcn  strips  or  wires  of  either  metal  are 
rendered  incandescent,  a  mild  and  pleasant  light  is  emitted, 
much  less  contracted  and  glaring  than  the  light  obtained  from 
carbon  pencils;  and  with  the  additional  advantage  also,  that 
no  vitiation  of  the  atmosphere  occurs,  and  the  amount  of  light, 
at  any  one  point,  can  be  made  as  small  as  may  be  desired. 

Platinum,  according  to  Mr.  Farmer,  affords  about  100  candle 
light  per  square  inch  of  incandescent  surface,  when  within  220° 
of  the  point  of  fusioii,  and  a  bar  or  wire  of  this  metal  can  be 
maintained  at  this  temperature  for  any  length  of  time  by  means 
of  a  .suitable  regulator  and  current.  Iridium  is  even  better 
adajitcd  for  illuminating  purposes  than  ])latinum,  as,  in  conse- 
quence of  its  higher  melting  point,  it  yields  more  light  })er 
square  inch  of  heated  surface. 

While  it  is  undoubtedly  true  that  the  light  obtained  in  this 
wav  is  not  the  most  advantageous  for  light-house  and  steamship 
purposes,  or  for  places  where  the  daz/.ling  light  of  the  arc  is 
required,  it  is  none  the  less  true  that  for  many  other,  and  espe- 
cially for  private  or  domestic  uses,  it  possesses  decided  iidvan- 
tages  over  the  carbon  licrht.  and  on  many  accounts— among 
wdiich  th(>  facility  attending  its  regulation  is  not  least — is  far 
preferable. 


111- 


Its 
ips 
ho 

arc 


INDEX 


ABROAD,  tlio  telephone.  Si. 
AccessoriuH  mid  couuectloiiH  of    tlio 

cnrboii  telepUoiii',  )i:i7. 
Anvil,  lianiiiier  luid  xllrrup,  5. 
Auipuru  uii   the  repulsion  of  dllTunrnt  ele- 

inuntM  of  a  current  for  cuch  oilier,  U."). 
Appllcutionri  of  the  phono^ruph,  :^).'>. 
Appt:calioii  of  pcrmuucut  iiiuijnut:!  to  tclc- 

pliiinu,  iOfJ. 
Appuraiiii  for  producing   undiilatory  ciir- 

reiiiH,  70. 
Artieiilutiiig  telcpliono,  fill. 
Arltetilaiu  ^peeeh,  truiixinisgioa  of,  100. 
Atmo-iplienc  vibrulions,  5. 
Ailantic  cable,  reaiutance  of,  8G. 
Aiifii^'rapliic  telegraphy,  (JU. 
Auditory  nerves,  ij. 
.\ustiu,  Charles  K.,  telephonic  experiments. 


HELi,,  Professor  A.  O.,  upeakinji  teloplione, 
l." ;  researclies  in  teleplioiiy,  51),  •'JO. 
Itell  aill,ai. 
lieutley,    Henry,    experiments    witli    tele- 

I>huno.s,  'ri^'). 
Ueatsons  researches  i  i  telephony,  53,  113, 

U>J,  Vii. 
Blake,  I'rofeasor  Eli  W.,  contributions  to  the 

speaking'  telephone,  3r4  ;  use  of  railway 

tr.icii  for.  70. 
OLiko,  IJr.  ciaionco  .1.,  experiments  with  a 

plionauio^rapii  made  uul  oi'  a  hiiiuau 

ear,  t)9. 
Bourseilles,  Charles,  proposed  telephone,  1-17. 
II  itt^er'-  Pulyteehnical  >iote;i.ilati,  Hi'. 
Ureguet's  teli-puoiio  and  telephonic  investi- 
gations, ^sr. 

CAiiBOM  telephone,  <i:>;  measuring  rcsist- 
aii  ■«  of,  3i ;  invention  iif,  'Hi, 

Cable,  workiui?  telephone  throiii;n,  8r. 

Centennial  exhibition  of  telephone.  71). 

Channini,',  Dr.  WillUni  t'.,  leleplionic  inven- 
tions, ~ii,  ar4. 

Characteristics  of  sound,  9") ;  of  tlie  phono- 
graph, sor. 

Condenser,  application  to  telephone,  .31. 

Combination  of  the  Morsj  and  liarmonic 
tel.-pnone,  lii7. 

Constriicti  m  of  the  telephone,  83,  20.3. 

Correlaiion  of  forjes,  4,'. 

Clarke,  Louis  VV.,  researches  and  experi- 
ments in  telegraphy.  Tli,  2,0. 

Current  induction,  arrangements  for  neu- 
traliziiii,',  302. 

Currents,  intermittent,  pulsatory  and  undii- 
latory, 54. 

Curreats  produced  in  the  telephone,  391, 


Dei.ezennk's  researches  in  telephony,  i>(i, 
117,  130. 

lie  la  Uive,  researches  In  telephony,  55,  112, 
131. 

niaphragm,  vibrating,  Ifi. 

Discharge  of  a  Leyilen  jar  through  an  iron 
wire  causes  the  wire  to  produce  a  sound, 
122. 

Dolbeai's,  Professor  A.  E.,  speaking  tele- 
phone, 10,  75  ;  researches,  2()<) ;  ma.'neto- 
electrie  telephone,  2IW ;  electrophone, 
2(17;  projective  Kpp.iratus,  2(i;l ;  converti- 
bility of  sound  into  electricity,  272. 

Du  Moncel's  researches  in  telephony,  5ti,  llli; 
theory  of  the  telephone,  2<i(j. 

TJIau.  human,  employed  as  a  phonauto- 
U     griipli,  tiO. 

Early  experiments  in  telephony  by  Elisha 
Uray,  1H5. 

Edison's  telephonic  researches,  218;  Carlmn 
telephone,  221 ;  talking  phonoL-raph.  292; 
electro-static  telephone,  2;j3;  electro-har- 
luouio  telegiaph,  lt)7 ;  thermo-electric 
telephone,  2;«  ;  quadruplex  telegraph, 
310;  electro-motograpli,  371. 

Effects  produced  by  resonant  devices.  183. 

Electrical  rheotorae,  119  ;  transmission  of 
speech,  llli. 

Electio-magnetic  piano,  52. 

Kleciro-motograph,  371. 

Klectro-harinonic  telegraphy,  235. 

Electrostatic  telephone,  2^11. 

Electric  call  bells,  .37.');  combination  keys, 
377 ;  apparatus  forgiving  the  signal,  379; 
Iho  viDr.iting  lieli,  380;  double  liells, 
!W2  ;  siiiile  Bells  to  be  worked  without 
inierrupling  the  circuit,  3*J ;  electric, 
alarm  with  relays.  38r  ;  Siemens  and 
Ualsko  station  alarm,  138.8 ;  Hreguet's 
alarm  or  call,  388  ;  combination  of  a 
single  call  with  two  or  more  rel  i.vs  for 
several  lines, .301 ;  Siemens's  and  llalske's 
relays  with  aiiniiiiciator  plate,  3J2 ; 
clock  work  alarm,  :i'X>. 

Electric  light,  40);  Urusli's  improved  car- 
bons, 427  ;  Brush's  dynamo-electric  m.i- 
chines,  423;  Brush's  autoinadc  regela- 
tors,  412;  cost  of  the  light.  42i);  Davy's 
experiments,  40);  Duboscii's  regulator, 
40;) ;  l-'ariner's  automatic  lamp,  400 ; 
Fanner's  dynamo-electric  machine,  42:); 
Foucaull's  regubitor,  4iK);  Oraiuine's 
machine,  421  ;  Uiirt's  lamp.  409  ;  Jali- 
loclikoll's  candle,  410;  I.add's  dynamo- 
electric  machine.  419  ;  mauiieto-electric 
machines.  413  ;  Siemens'sarmature,  417  ; 
subdivision  of  the  light,  427 ;  tempera- 
ture of  tiiu  arc,  401, 


480 


INDEX. 


F 


oniiKii's  law  of  vihratloiml  foriiiH,  ai9. 


GALVANIC  milBic,  110. 
Gosslot'H  resL'iirches  in  tc.leplioiiy,  55, 
117. 

Galilco'B  observations,  SHIi. 

(iay-l-UHHac's  difcovericx,  123. 

Gorf'sreHuarclici',  5(1. 

Oower'B,  F.  A.,  f.x|)i'riinent»,  SO. 

Gottoin  dt!  Comma's  oljHcrvations,  129. 

Gray,  Ellsha,  teleplionlc  ronearcliiin,  151,171; 
clectro-lianiioiiic  Irli'iilioiii',  W7  ;  early 
t'xperlmi'iitH  in  ti'lepliony,  IS')  ;  l)iitli-tiil) 
e.YJxTimunts,  1H7 ;  violin  cxpiTinii'nt, 
188  ;  plienomcna  attending  tlie  tr,ii]<- 
niission  of  vibratory  curreiitw.  171  ;  dis- 
covery of  tlie  Hpeakiiif;  telepliorn',  LI ; 
transinlHsion  of  eomposlte  tones,  ISil ; 
telephonic  Bpecifleations  Hied  in  tlie 
United  States  I'atcnt  OIHce,  February 
14.  187«,  217. 

Graphical  method  of  physicists,  215. 

Graham,  I'rofesso',  theory  of  vibration  of 
Trevelyan's  liars,  11.5. 

Grove's  experiment  denionstraliii);  the  ten- 
dency of  the  particles  of  ma;;iietic  bodies 
to  yronp  themselves  under  the  liilluenee 
of  nuii^netism  in  a  loni;itudMial  or  axial 
direction,  128. 

Guillemin's  researchea  in  telephony,  .55,  112, 
123, 

HENRY,  Professor  Joseph,  telephonic  re- 
searches, 14. 
Uelmholt/.  on  the  human  voice,  48 ;  ana- 
lysis of  the  vowel  sounds,  51,  <l'i  ;  of 
vocal  sounds,  2.55  ;  method  of  analy/.ing 
tones  transmitted  throui;!!  a  wire.  161. 
Hamoroiis  t^xani  i)le  of  tc^lephonic  expectancy 
related  by  W.  U.  Preece,  82. 

INnuoTiov  currents,  87,  101. 
Inlluenco    of   molecular    actions    upon 
magnetism,  produced  by  dynamic  electri- 
city, 131. 
Induced  currents,  reactive  effect  of,  17!). 
Invention  of  the  speaking'  telepbone,  201. 
Improvements  by  ('banning,  Hlal;e,  I'eirce, 
Jones  and  Austin,  .i75. 

Janniab's  telephonic  researches,  55. 
Joule's   researches   in   telephony,   .55  ; 
inllucnce  of  niugnetism  over  dimensions 
of  Imdies,  12:). 
Jouos,    Edison    S.,  invantiou  of  telephone 
handle,  276. 

KNioiiT's  American  dictionary,  cuts  from, 
Ull,  2!»,  2!)7. 
KOnig's  researclies,  68  ;    plionograph,   205 ; 
mouometrio  flames,  21(0. 

I    A  Conn's  telephone,  62. 
J    Laborde's  telephonic  researches,  .55. 
Legat's  telepboniu  investigations  and  pub- 
lications, .55. 
Logograph  invented  by  W.  II.  Harlow,  F.  I{. 

S.,  205. 
Logographic  records,  207  ;  wiih  the  human 
ear,  298. 


MAOoi's  heat  experlmenls,  i:«. 
.Mariuninl's  experlmruts,  i:V<. 

Magnetic  c(M"es  for  tt'lrpiione-*,  177. 

Magnetic  speaking  telephone,  221. 

Alanium'tric  capsule,  W. 

Maurey's  experiments,  68. 

Matteucci  s  experiments,  55.  112. 

Marrlan's  researches,  55,  112,  117. 

.Magneto-electric  nmehine,  28. 

Membrane,  elastic,  6. 

Miirse  telegra|)h  contrasted  with  the  tele- 
phone, 84. 

Molecular  forces  disturbed  by  magnetism, 
111  ;  action  of  magnetic  bodies,  117,  121. 

Multiple  telegraphy,  .57 

Mayers.  I'rofessor  A.  M.,  magnKled  tracings 
on  smoked  glass  of  the  talking  phono- 
graph record  on  tile  f>ill,  U(KI ;  what  the 
lorm  of  the  trace  depends  upon,  ijo^l. 


]^ 


ici.K's  tubular  electro-magnet,  101. 


OHM,  or  unit  of  resistance,  lO:). 
On  the  disturbance  of  molecular  forcei 
by  magnetism,  HI. 
On  the  convertibility  of  sound  Into  elec- 
tricity, 2;2. 

PAOK,  Dr.  Charles  fi.,  researches  in  tele- 
phony, 11(1,  117,2,).'. 

Peirce,  Professor  John,  experiments  and  In- 
ventions, 76,  271. 

Peculiarities  of  vibratory  currents,  K.l ;  of 
coinpoun  1  vibraiions,  217. 

Phelp.s'a  telephone,  21. 

Phonograph,  ihe  talking.  203;  monndng  of 
the.  ;*)1  ;  what  clearness  of  articulation 
depends  nnon.  IWl. 

Phon  lutograph,  Jiurlow's,  205  ;  KfSnig,  205 ; 
Scott's.  205;  experiments  with,  liH. 

Phonographic  records,  tracings  from,  303; 
diauias  ;  letiers,  305. 

Pill  hot  leleplione.  00. 

Plate,  indexible,  ;17. 

Poggendorff  s  nsearches  in  telephony,  55. 

Providence  e.\periineiita  i»ts.  76,  274. 

Preece,  W.  11  ,  observations  on  the  tele- 
phone, 82. 

Production  of  vocal  sounds,  181. 

Properties  of  the  pendnlum.  237. 

Producing  the  record  of  sound,  204, 

UADndiM.EX  telegraphy,  30!l ;  bridge 
method,  313;  differential  method,  315 ; 
combined  dilTereiilial  aid  bridge  meth- 
ods, 321 ;  iirrangemeiit  of  apparatus  for 
long  circuits,  325  ;  double  acting  relay, 
320  ;  single  current  tiausiiiitter,  3)8,339  ; 
adjustinentof  the  quad  uplex,  :Ul  ;  com- 
bined quadruple.^  and  duplex  circuiis, 
315 ;  arrangement  for  coiitraplex  trans- 
inis-ion,  317;  combined  diplex  und  coii- 
traplex 8  stems,  310;  combined  diplex 
and  coiitraplex  systems,  319,  .H5I  ;  com- 
bination of  ipiiidriiplex  and  duplex  sys- 
tem-', 3">3  ;  qiiadrnplex  repeater,  3.'>5,  357  ; 
improved  rc'iav,  3W  ;  directions  fo  ■  set- 
ting up  he  ipiadriiplex.  3(6  ;  the  double 
current  transmitter.  3:)(i ;  the  compound 
polarized  relay,  3:)8  ;  th  single  polaii/cil 
riday.  310  ;  'idjiistment  of  the  apparatus 
for  working,  311  ;  combination  of  quad- 


Q 


v» 


INUEX. 


431 


<* 


niplcx  mill  (liplrx  »v»t('iiis,  liW:  nr- 
niN^'riniMil  riii'liraiicli  iitlleoH,  Uj!)  ;  i|imil- 
ni|iU:\  uiid  Hiii^'lt!  circuit  rnnililiiutiiin, 
.'liil  ;  iirriiii<;ciiiuiit  fur  iii'iilruli/.iii);  cur- 
rent iiiiliictiiin,  .'11)3;  iiiiliictli'ii  butwot'ii 
iiHrallel  Iiiich,  .11)1  ;  (luiiblu  trav.MniHxiun 
III  ilifsimuMilroctioii,  .'itit ;  otrly  mt'tnodH 
•irHliiiiiltunuiiUijtrunMiiiiHHioii  In  tlii'  Hniiiu 
(lirt'ctiiiii,  31)4 ;   UuriiiitdU;  h  iiiutlioil,  310), 

REACTIVE  cfteit  of  indiici'il  oiirreiitK,  178. 
KuNOIIHIIt  tluvici!!',  liiruCiN  of,    Wi. 

Hemarks  iiii  lli  •  llicory  of  the  teleplioiio,  3.S9. 

U.-eulv('ri<.  ti'le|)liiiiiic,  3I!I. 

KiwarcliuH  in   ti;le|,'ra|<liy  by  Kdlson,  218; 

IJdlxM,  .5.').  •Si\. 
TliiiHu'd  tfli'lilionc,  2,')I. 
UbODtoiiU',  TH. 
Uulinikorli'H  coil,  7S. 

SALKM  lecture  reported  by  telephone,  78. 
Silvettown  Ciiiiipany,  !)1. 

Scott  H   Leon,  plniiiDijrapli.  tH,  2(15. 

Si);nalliMK  appunitiis  for  teiepbones,  20,  229. 

Sound,  cliaracleri.-<ti(s  of,  7,  !(,),  293  ;  con- 
verllbility  inln  electricity,  Krap'iic  rep- 
leselitationHOf,  H  ;  velocity  of,  2)3  ;  Tyii- 
Ua  I'll  leciureKon,  2111 ;  Hound  waves  con- 
verted into  heat  waves,  2;J-1  ;  vilirutiond 
of,  5. 

Sounds  of  the  hiimun  voice,  !I7  ;  Ilelinlioltz, 
anulyi-is  of  vocal,  2.V);  produced  In  iron 
wir.!  by  pa-'siige  of  electricity,  122  ;  pro- 
duced by  niiileciilar  (banjoes,  2.')3. 

Honoroui*  u  diiiationK,  U'.t. 

Specific  itioiiH  of  t'lephonic  inventions  flied 
in  the  Utiiied  Siuies  Patent  Olllce,  Keh- 
riiary  14,  lH7(i;  Gray's,  2«U;  ile  I's,  205. 

Speakini  telephone,  invention  of,  201. 

Sympathetic  vibrations,  67. 

TAi.TiiNO  phonograph,  2!)2. 
Ti.leplKine,articulatiiii;,  15;  andibllity  of, 
88;  American  sp'tikiii),' company,  46  ;  a|>- 
plicatioii  of  p^-rmaneni  niai;iiets  to,  2.VJ  ; 
uccussories  and  connections  of  the  c;ir- 
hon,  22r;  Hell's,  17,50,21)5;  battery,  32 ; 
Bailie's,  47;  Hreijuet's,  2Sr ;  Hour.seillu's, 
147;  Hentley's experiments. 225;  cirrelu- 
tion  of  fore  -a  llhHtrated  by,  42 ;  carbon, 
34,  223;  C'lveat  for,  217;  currents  pro- 
duced in,  21»1 ;  conversation  of  Kiiglish 
Hcientists  about.  8i;  fhanuiti!?,  Dr.  Wil- 
liam F.,  inventions,  2r7;  Uolliear's,  lit, 
75  ;  double  diaphrai.'in,  33  ;  duplex,  21  ; 
diBtanceover  which  it  can  be  worked.  Ml  ; 
'Sdlson  3^ ;  Kdison's  ri'searchei.  218 ; 
electro  -  static,  2.31;  electro  •  harmonic, 
)i)7;  (iray's.  15.  73;  Uray's  tolepliotiic 
researches,  1,52  ;  (Jray'selectro-harinoiiic, 
11)7  ;  tirav's  caveat.  217  ;  hanille,  27li ; 
iunumurablu  uaun  of,  45 ;  llmsirutiuu  of 


correlation  of  fornen  by  the,  ■12  ;  improve- 
ments tjy  flniiiniiu,',  Ulake.  IVirce  and 
•lonits,  2i'5  ;  K.  S.  .Jones,  liundle,  27ti  ; 
limit  of  audibility,  38  ;  inu-lcal,  »  ;  Morse 
comlilnatlon,  41  ;  magneto,  221;  magnetic 
cores  for,  177 ;  I'help'H  duplex,  21  ; 
Peirce's  inoiithiilece  for.  275  ;  pill  box, 
no ;  Kelss's,  !t,  148,  251  ;  reiieater,  3«  ;  re- 
ceivers, 193, 21'J;  remarkable  phenomena, 
3S1  ;  siphon  recorder,  279 ;  Kiiniallini; 
apt) trains,  29,  tM  ;  sensilivenessof, 385  ; 
switch,  10;  speaking,  invention  of,  201; 
Thomson's  report,  93  ;  tones  proiliiced 
by  electric  currents.  111,  1.39  ;  theory  of, 
288  ,  vibratory  bell,  41  ;  vi.bratint,'  dia- 
pliraj,'!!!,  Itt  ;  vibratory  plate,  48  ;  work- 
iuu  tliriiiii.'h  cable,  HI. 

Tone,  li ;  simple  and  composite,  8. 

Tracings  of  mr  vibrations,  91 ;  from  phono- 
(jraph  records,  31)3. 

Transmission  of  composite  tones,  189. 

'i'ransmitlini:  reeds,  191. 

Tyudull's  experiments,  156 ;  lectures  on 
sound,  240. 

U9KS  of  the  phonoifraph,  30.). 
Uudiilatory  currents,  5:1,  85,  208. 
Ijulveroity,  Boston,  72. 

yAiii.Ev.  Croinwell  F.,  researches,  t;2. 
Various  forms  of  transmitliuj;  reeds, 
191  ;    telephonic    receivers,  1H3 ;    traus- 
iiiitters,  197. 

Velocity  of  sound,  213. 

Vlbratin?  plate,  48  ;  rods,  2,39. 

Vibratory  circuit  breaker,  59  ;  movements 
and  inol.Tuiar  effects  determined  in  niaij!- 
netic  bodies  by  the  inttuence  of  electric 
currents,  117  ;  lurrenls.  peculiarities  of, 
173  ;  motions  of  fluids,  211. 

Vibrations,  propai;atioii  of  compound.  247 ; 
of  Trevelya  c's  bars  by  the  galvanic  cur- 
rent, 113;  of  sound,  optically  exhibited, 
fi8. 

Vibnitional  forms,  Fourier's  law  of,  249. 

Visible  speech,  68. 

WAOESEii's  hammer,  140. 
Watson's.  Thonas  A.,  assistance  in 

perfectluKthi'  speakins;  telephone,  71,  77. 
Wartmann's  re-earches  in  telephony,  .5.5,  113. 
Wertheini's  researches  in  telephony.  .V) ;  on 

the  elasticity  of    metals,   123  ;  uiialysia 

of  the  mechanical  effects  manifested  iu 

miignetism.  lit,  128,  139. 
Western  Kl  ctric   .Manufacturing  Company 

telephonic  apparatus.  31,  32,  33. 
WorKlni;  telepho  ie.i  over  artillclal  lines,  103. 
Wheat  tone's  instruments.  104. 
Wil-on's.  Charles  11.,  method  for  overcom- 

in)(  current  luductiou,  362. 


